bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural Domains of the CB1 Cannabinoid Receptor That Contribute to Constitutive Activity and G-Protein Sequestration
Authors: Nie Jingjiang , Lewis Deborah L.
Published: April 2018

The CB1 cannabinoid receptor is a constitutively active receptor that can sequester Gi/o-proteins and prevent other Gi/o-coupled receptors from signaling (Bouaboula et al., 1997; Pan et al., 1998; Vasquez and Lewis, 1999). G-protein sequestration occurs because the population of CB1 cannabinoid receptors exists in both an inactive G-protein-precoupled RGGDPstate and a constitutively active R*GGTPstate. We tested the hypothesis that the distal C-terminal tail acts to prevent G-protein activation. We found that truncation of the distal C-terminal tail of the CB1 receptor (CB1–417) enhanced both the constitutive activity and the ability of the receptor to sequester G-proteins. In addition, we tested the hypothesis that the conserved aspartate (D2.50) in the second transmembrane domain of the CB1 cannabinoid receptor is crucial for constitutive activity and G-protein sequestration. We found that the mutation of aspartate to asparagine (CB1-D164N) abolished G-protein sequestration and constitutive receptor activity without disrupting agonist-stimulated activity. We conclude that the CB1-D164N mutation and the C-terminal truncation shift the population of receptors in opposite directions. The CB1-D164N mutation shifts the receptor into an inactive R state upcoupled from G-proteins, whereas the C-terminal truncation (CB1–417) shifts the receptor into the active R*GGTPstate. Thus the distal C-terminal tail acts to constrain the receptor from activating G-proteins, whereas the aspartate (D2.50) in the second transmembrane domain stabilizes the receptor in both the inactive RGGDPstate and the active R*GGTPstate.
Specific Neurotrophic Factors Support the Survival of Cortical Projection Neurons at Distinct Stages of Development
Authors: Catapano Lisa A. , Arnold Matthew W. , Perez Francisco A. , Macklis Jeffrey D.
Published: April 2018

Repair of specific neuronal circuitry in the neocortex may be possible via neural precursor transplantation or manipulation of endogenous precursorsin situ. These approaches will almost certainly require a detailed understanding of the mechanisms that control survival and differentiation of specific neuronal lineages. Such analysis has been hampered by the overwhelming diversity of neuronal types intermixed in neocortex and the inability to isolate individual lineages. To elucidate stage-specific controls over the survival of individual lineages of cortical neurons, we purified immature callosal projection neurons (CPN) at distinct stages of development from embryonic and postnatal mouse cortex by retrograde fluorescence labeling, followed by fluorescence-activated cell sorting. Purified CPN survive well in culture, acquire stage-specific projection neuron morphologies, and express appropriate neurotransmitters and growth factor receptors. Purified CPN are dependent on exogenous trophic support for survival in a stage-specific manner. Survival of postnatal day 2 (P2) to P3 and P6–P7 CPN is promoted by overlapping but distinct sets of neurotrophic factors, whereas embryonic day 19 CPN show less specificity of dependence on peptide factors. These studies demonstrate for the first time the stage-specific control by peptide growth factors over the survival of a specific cortical neuronal lineage. Such information may be critical for the future goal of directed differentiation of transplanted or endogenous precursors toward cellular repair of complex cortical circuitry.
Sensory and Multisensory Responses in the Newborn Monkey Superior Colliculus
Authors: Wallace Mark T. , Stein Barry E.
Published: April 2018

Superior colliculus (SC) neurons have the ability to synthesize information from different sensory modalities, resulting in enhancements (or depressions) of their activity. This physiological capacity is, in turn, closely tied to changes in overt attentive and orientation responses. The present study shows that, in contrast to more altricial species, many deep layer SC neurons in the rhesus monkey are multisensory at birth. Such neurons can respond to stimuli from different sensory modalities, and all convergence patterns seen in the adult are represented. Nevertheless, these neurons cannot yet synthesize their multisensory inputs. Rather, they respond to combinations of cross-modal stimuli much like they respond to their individual modality-specific components. This immature property of multisensory neurons is in contrast to many of the surprisingly sophisticated modality-specific response properties of these neurons and of their modality-specific neighbors. Thus, although deep SC neurons in the newborn have longer latencies and larger receptive fields than their adult counterparts, they are already highly active and are distributed in the typical adult admixture of visual, auditory, somatosensory, and multisensory neurons. Furthermore, the receptive fields of these neurons are already ordered into well organized topographic maps, and the different receptive fields of the same multisensory neurons show a good degree of cross-modal spatial register. These data, coupled with those from cat, suggest that the capacity to synthesize multisensory information does not simply appear in SC neurons at a prescribed maturational stage but rather develops only after substantial experience with cross-modal cues.
Spontaneous Activity in Developing Ferret Visual CortexIn Vivo
Authors: Chiu Chiayu , Weliky Michael
Published: April 2018

Multi-electrode extracellular recordings in area 17 of awake behaving ferrets were conducted to characterize the pattern of spontaneous activity in the developing visual cortex before eye opening. A linear array of 16 microwire electrodes was used to record extracellular neuronal activity across a 3.2 mm strip of visual cortex between postnatal days 22 and 28. Whereas synchronous bursts of activity were observed at all recording sites, cross-correlation analysis revealed that the timing of spike activity at all electrodes was not precisely correlated. Correlated activity between cortical sites exhibited a patchy organization having long-range components. Long-range correlated activity was observed between cortical patches that were separated by a mean distance of 1 mm. The spatial pattern of correlated activity persisted during transient lateral geniculate nucleus (LGN) activity block, indicating that long-range correlated activity is generated by intrinsic circuits within the cortex, independent of LGN input activity. These results demonstrate an innate patchy organization of correlated spontaneous activity within the cortex during the early development of cortical functional and anatomical organization.
Sorting of Internalized Neurotrophins into an Endocytic Transcytosis Pathway via the Golgi System: Ultrastructural Analysis in Retinal Ganglion Cells
Authors: Butowt Rafal , von Bartheld Christopher S.
Published: April 2018

Subcellular pathways and accumulation of internalized radiolabeled neurotrophins NGF, BDNF, and NT-3 were examined in retinal ganglion cells (RGCs) of chick embryos by using quantitative electron microscopic autoradiography. All three neurotrophins accumulated in endosomes and multivesicular bodies. BDNF and NGF also concentrated at the plasma membrane, whereas NT-3 accumulated transiently in the Golgi system. The enhanced targeting of NT-3 to the Golgi system correlated with the anterograde axonal transport of this neurotrophin. Anterograde transport of NT-3, but not its internalization, was significantly attenuated by the tyrosine kinase (trk) inhibitor K252a. Abolishment of trk activity with K252a shifted NT-3 (and BDNF) away from the Golgi system and into a lysosomal pathway, indicating that trk activity regulated sorting of the ligand-receptor complex. Cross-linking of neurotrophins and immunoprecipitation with antibodies to the neurotrophin receptors p75, trkA, trkB, and trkC showed that the large majority of exogenous, receptor-bound NT-3 was bound to trkC in RGC somata, but during anterograde transport in the optic nerve most receptor-bound NT-3 was associated with p75, and after arrival and release in the optic tectum transferred to presumably postsynaptic trkC. These results reveal remarkable and unexpected differences in the intracellular pathways and fates of different neurotrophins within the same cell type. They provide first evidence for an endocytic pathway of internalized neurotrophic factors via the Golgi system before anterograde transport and transcytosis. The results challenge the belief that after internalization all neurotrophins are rapidly degraded in lysosomes.
Impact of Early Deafness and Early Exposure to Sign Language on the Cerebral Organization for Motion Processing
Authors: Bavelier Daphne , Brozinsky Craig , Tomann Andrea , Mitchell Teresa , Neville Helen , Liu Guoying
Published: April 2018

This functional magnetic resonance imaging study investigated the impact of early auditory deprivation and/or use of a visuospatial language [American sign language (ASL)] on the organization of neural systems important in visual motion processing by comparing hearing controls with deaf and hearing native signers. Participants monitored moving flowfields under different conditions of spatial and featural attention. Recruitment of the motion-selective area MT–MST in hearing controls was observed to be greater when attention was directed centrally and when the task was to detect motion features, confirming previous reports that the motion network is selectively modulated by different aspects of attention. More importantly, we observed marked differences in the recruitment of motion-related areas as a function of early experience. First, the lateralization of MT–MST was found to shift toward the left hemisphere in early signers, suggesting that early exposure to ASL leads to a greater reliance on the left MT–MST. Second, whereas the two hearing populations displayed more MT–MST activation under central than peripheral attention, the opposite pattern was observed in deaf signers, indicating enhanced recruitment of MT–MST during peripheral attention after early deafness. Third, deaf signers, but neither of the hearing populations, displayed increased activation of the posterior parietal cortex, supporting the view that parietal functions are modified after early auditory deprivation. Finally, only in deaf signers did attention to motion result in enhanced recruitment of the posterior superior temporal sulcus, establishing for the first time in humans that this polymodal area is modified after early sensory deprivation. Together these results highlight the functional and regional specificity of neuroplasticity in humans.
Anatomical Distribution and Cellular Basis for High Levels of Aromatase Activity in the Brain of Teleost Fish: Aromatase Enzyme and mRNA Expression Identify Glia as Source
Authors: Forlano Paul M. , Deitcher David L. , Myers Dean A. , Bass Andrew H.
Published: April 2018

Although teleost fish have higher levels of brain aromatase activity than any other vertebrate group, its function remains speculative, and no study has identified its cellular basis. A previous study determined aromatase activity in a vocal fish, the plainfin midshipman (Porichthys notatus), and found highest levels in the telencephalon and lower levels in the sonic hindbrain, which was dimorphic between and within (males) sexes. We have now localized aromatase-containing cells in the midshipman brain both by immunocytochemistry using teleost-specific aromatase antibodies and byin situhybridization using midshipman-specific aromatase probes. Aromatase-immuno-reactivity and mRNA hybridization signal are consistent with relative levels of aromatase activity in different brain regions: concentrated in the dimorphic sonic motor nucleus, in a band just beneath the periaqueductal gray in the midbrain, in ventricular regions in the hypothalamus, and highest levels in the telencephalon especially in preoptic and ventricular areas. Surprisingly, double-label immunofluorescence does not show aromatase-immunoreactive colocalization in neurons, but instead in radial glia throughout the brain. This is the first study to identify aromatase expression mostly, if not entirely, in glial cells under normal rather than brain injury-dependent conditions. The abundance of aromatase in teleosts may represent an adaptation linked to continual neurogenesis that is known to occur throughout an individual's lifetime among fishes. The localization of aromatase within the intersexually and intrasexually dimorphic vocal-motor circuit further implies a function in the expression of alternative male reproductive phenotypes and, more generally, the development of natural, individual variation of specific brain nuclei.
The Role of Activity-Dependent Network Depression in the Expression and Self-Regulation of Spontaneous Activity in the Developing Spinal Cord
Authors: Tabak Joël , Rinzel John , O'Donovan Michael J.
Published: April 2018

Spontaneous episodic activity occurs throughout the developing nervous system because immature circuits are hyperexcitable. It is not fully understood how the temporal pattern of this activity is regulated. Here, we study the role of activity-dependent depression of network excitability in the generation and regulation of spontaneous activity in the embryonic chick spinal cord. We demonstrate that the duration of an episode of activity depends on the network excitability at the beginning of the episode. We found a positive correlation between episode duration and the preceding inter-episode interval, but not with the following interval, suggesting that episode onset is stochastic whereas episode termination occurs deterministically, when network excitability falls to a fixed level. This is true over a wide range of developmental stages and under blockade of glutamatergic or GABAergic/glycinergic synapses.

We also demonstrate that during glutamatergic blockade the remaining part of the network becomes more excitable, compensating for the loss of glutamatergic synapses and allowing spontaneous activity to recover. This compensatory increase in the excitability of the remaining network reflects the progressive increase in synaptic efficacy that occurs in the absence of activity. Therefore, the mechanism responsible for the episodic nature of the activity automatically renders this activity robust to network disruptions. The results are presented using the framework of our computational model of spontaneous activity in the developing cord. Specifically, we show how they follow logically from a bistable network with a slow activity-dependent depression switching periodically between the active and inactive states.
Norepinephrine Secretion in the Hypothalamic Paraventricular Nucleus of Rats during Unlimited Access to Self-Administered Nicotine: AnIn VivoMicrodialysis Study
Authors: Fu Yitong , Matta Shannon G. , Brower Victoria G. , Sharp Burt M.
Published: April 2018

Norepinephrine (NE) secretion within the hypothalamic paraventricular nucleus (PVN) is pivotal to endocrine and behavioral responses. Activation of NE afferents to PVN also is necessary for the hypothalamo–pituitary–adrenal axis response to passively administered nicotine. The mode of drug delivery is a critical determinant of the dynamics of neurotransmitter secretion, yet the PVN NE response to nicotine self-administration (SA) is unknown. Herein, rats housed in operant chambers had unlimited 23 hr access to self-administered nicotine.In vivomicrodialysis of PVN NE was performed, collecting consecutive 7 min samples over 9 hr sessions during three phases of nicotine SA: acquisition (day 1); early maintenance, once stable rates of SA were achieved (day 9.2 ± 0.6); later maintenance (day 18.6 ± 0.8). On d1, nicotine animals had an increased percentage of SA episodes (SAEs) in which NE levels were elevated (80 vs 30% with saline;p< 0.01). By early maintenance, a fourfold increase in such episodes was observed in nicotine animals (p< 0.01), and the overall NE level was greater (1.30 ± 0.24 vs 0.63 ± 0.07 pg/10 μl in saline;p< 0.05); NE increased during the first, but not the last, SAE. The pattern was similar during later maintenance, although NE responsiveness declined (overall NE level, 0.96 ± 0.19 in nicotine vs 0.52 ± 0.08 pg/10 μl in saline;p< 0.05). Therefore, nicotine SAEs were associated with sustained increases in NE secretion during all three phases of SA. However, the reduced NE responsiveness observed both within the dialysis session in each phase and by later versus early maintenance is consistent with progression of partial daily desensitization of PVN NE secretion to nicotine SA. Therefore, in rats chronically self-administering nicotine, the drug stimulates sustained PVN NE secretion that may alter neuroendocrine and behavioral responses mediated by the PVN. Compared with studies of chronic human smokers, our nicotine SA model may reflect the CNS noradrenergic responses that occur during human cigarette smoking.
Combined Effects of Intrinsic Facilitation and Modulatory Inhibition of Identified Interneurons in the Siphon Withdrawal Circuitry ofAplysia
Authors: Bristol Adam S. , Fischer Thomas M. , Carew Thomas J.
Published: April 2018

Synaptic plasticity can be induced through mechanisms intrinsic to a synapse or through extrinsic modulatory mechanisms. In this study, we investigated the relationship between these two forms of plasticity at the excitatory synapse between L29 interneurons and siphon motor neurons (MNs) inAplysia. Using isolated ganglia, we confirmed that the L29–MN synapses exhibit a form of intrinsic facilitation: post-tetanic potentiation (PTP). We also found that L29–MN synapses are modulated by exogenous application of 5-HT: they are depressed after 5-HT exposure. We next investigated the functional relationship between an intrinsic facilitatory process (PTP) and extrinsic inhibitory modulation (5-HT-induced depression). First, we found that application of 5-HT just before L29 activation results in a reduction of PTP. Second, using semi-intact preparations, we found that tail shock (TS) mimics the effect of 5-HT by both depressing L29 synaptic transmission and by reducing L29 PTP. Third, we observed a significant correlation between L29 activity during TS and subsequent synaptic change: low-responding L29s showed synaptic depression after TS, whereas high-responding L29s showed synaptic facilitation. Finally, we found that we could directly manipulate the sign and magnitude of TS-induced synaptic plasticity by controlling L29 activity during TS. Collectively, our results show that the L29–MN synapses exhibit intrinsic facilitation and extrinsic modulation and that the sign and magnitude of L29–MN plasticity induced by TS is governed by the combined effects of these two processes. This circuit architecture, which combines network inhibition with cell-specific facilitation, can enhance the signal value of a specific stimulus within a neural network.
Consolidation of Extinction Learning Involves Transfer from NMDA-Independent to NMDA-Dependent Memory
Authors: Santini Edwin , Muller Robert U. , Quirk Gregory J.
Published: April 2018

Extinction of conditioned fear to a tone paired with foot shock is thought to involve the formation of new memory. In support of this, previous studies have shown that extinction of conditioned fear depends on NMDA receptor-mediated plasticity. To further investigate the role of NMDA receptors in extinction, we examined the effects of the NMDA antagonistd(−)-3-(2-carboxypiperazine-4-yl)-propyl-1-phosphonic acid (CPP) on the extinction of conditioned freezing and suppression of bar pressing (conditioned emotional response). Rats extinguished normally during a 90 min session in the presence of systemic CPP (10 mg/kg), but were unable to recall extinction learning 24 hr later. This suggests that an NMDA-independent form of plasticity supports short-term extinction memory, but NMDA receptors are required for consolidation processes leading to long-term extinction memory. Surprisingly, extinction learned in the presence of CPP was recalled normally when tested 48 hr after training, suggesting a delayed consolidation process that was able to improve memory in the absence of further training. Delayed consolidation involves NMDA receptors because CPP injected on the rest day between training and test prevented 48 hr recall of extinction learned under CPP. Control experiments showed that the effect of CPP on memory consolidation was not caused by state-dependent learning or reduced expression of freezing under CPP. These findings demonstrate that NMDA receptor activation is critical for consolidation of extinction learning and that this process can be initiated after training has taken place. We suggest that consolidation of extinction involves off-line relearning that reinforces extinction memory through NMDA-mediated plasticity, perhaps in prefrontal–amygdala circuits.
Cloning, Expression, and Regulation of a Glucocorticoid-Induced Receptor in Rat Brain: Effect of Repetitive Amphetamine
Authors: Wang Danzhao , Herman James P. , Pritchard Laurel M. , Spitzer Rebecca H. , Ahlbrand Rebecca L. , Kramer Gerald L. , Petty Frederick , Sallee Floyd R. , Richtand Neil M.
Published: April 2018

Behavioral sensitization to psychostimulants involves neuroadaptation of stress-responsive systems. We have identified and sequenced a glucocorticoid-induced receptor (GIR) cDNA from rat prefrontal cortex. The full-length GIR cDNA encodes a 422 amino acid protein belonging to G-protein-coupled receptor superfamily. Although the ligand for GIR is still unknown, the dendrogram construction indicates that GIR may belong to peptide receptor subfamily (e.g., substance P receptor), with more distant relationship to subfamilies of glycoprotein hormone receptors (e.g., thyrotropin receptor) and biogenic amine receptors (e.g., dopamine receptor). GIR shares 31–34% amino acid identity to the tachykinin receptors (substance P receptor, neurokinin A receptor, and neurokinin B receptor). GIR mRNA is expressed preferentially in brain, and its neuronal expression is relegated to limbic brain regions, particularly in forebrain. GIR transcript levels are increased significantly and persistently in prefrontal cortex for 7 d after discontinuation of chronic amphetamine exposure. The induction of GIR expression by amphetamine is associated with augmented behavioral activation. These findings suggest that modulation of GIR expression may be involved in behavioral sensitization, and GIR may play a role at the interface between stress and neuroadaptation to psychostimulants.
Repeated Cocaine Administration Attenuates Group I Metabotropic Glutamate Receptor-Mediated Glutamate Release and Behavioral Activation: A Potential Role for Homer
Authors: Swanson Chad J. , Baker David A. , Carson Dan , Worley Paul F. , Kalivas Peter W.
Published: April 2018

The present study aimed to characterize a functional role for group I metabotropic glutamate receptors (mGluRs) in the nucleus accumbens and the capacity of repeated cocaine to elicit long-term changes in group I mGluR function. Reverse dialysis of the group I agonist (RS)-3,5-dihydroxyphenylglycine (DHPG) into the nucleus accumbens resulted in an increase in extracellular glutamate levels that was mediated by the mGluR1 subtype and depended on voltage-dependent Na+and Ca2+conductance. At 3 weeks after discontinuing 1 week of daily cocaine injections, the capacity of DHPG to induce glutamate release was markedly reduced. Similarly, DHPG induced an mGluR1-dependent increase in locomotor activity after microinjection into the nucleus accumbens that was significantly blunted 3 weeks after repeated cocaine administration. Signaling through group I mGluRs is regulated, in part, by Homer proteins, and it was found that the blunting of group I mGluR-induced glutamate release and motor activity after repeated cocaine was associated with a reduction in Homer1b/c protein that was selective for the medial nucleus accumbens. These data show that repeated cocaine produces an enduring inhibition of the neurochemical and behavioral consequences of stimulating mGluR1 that is accompanied by changes in the mGluR scaffolding apparatus.
Expression of cGMP-Specific Phosphodiesterase 9A mRNA in the Rat Brain
Authors: Andreeva Svetlana G. , Dikkes Pieter , Epstein Paul M. , Rosenberg Paul A.
Published: April 2018

cGMP has been implicated in the regulation of many essential functions in the brain, such as synaptic plasticity, phototransduction, olfaction, and behavioral state. Cyclic nucleotide phosphodiesterase (PDE) hydrolysis of cGMP is the major mechanism underlying the clearance of cGMP and is likely to be important in any process that depends on intracellular cGMP. PDE9A has the highest affinity for cGMP of any PDE, and here we studied the localization of this enzyme in the rat brain usingin situhybridization. PDE9A mRNA is widely distributed throughout the brain with varying regional expression. The pattern of PDE9A mRNA expression closely resembles that of soluble guanylyl cyclase (sGC) in the rat brain, suggesting a possible functional association or coupling of these two enzymes in the regulation of cGMP levels. Most of the brain areas expressing PDE9A mRNA also contain neuronal nitric oxide synthase (NOS), the enzymatic source of NO and the principal activator of sGC. PDE9A is the only cGMP-specific PDE with significant expression in the forebrain, and as such is likely to play an important role in NO–cGMP signaling.
Protein Kinase Modulation of a Neuronal Cation Channel Requires Protein–Protein Interactions Mediated by an Src homology 3 Domain
Authors: Magoski Neil S. , Wilson Gisela F. , Kaczmarek Leonard K.
Published: April 2018

Accumulating evidence suggests that many ion channels reside within a multiprotein complex that contains kinases and other signaling molecules. The role of the adaptor proteins that physically link these complexes together for the purposes of ion channel modulation, however, has been little explored. Here, we examine the protein–protein interactions required for regulation of anAplysiabag cell neuron cation channel by a closely associated protein kinase C (PKC). In inside-out patches, the PKC-dependent enhancement of cation channel open probability could be prevented by the src homology 3 (SH3) domain, presumably by disrupting a link between the channel and the kinase. SH3 and PDZ domains from other proteins were ineffective. Modulation was also prevented by an SH3 motif peptide that preferentially binds the SH3 domain of src. Furthermore, whole-cell depolarizations elicited by cation channel activation were decreased by the src SH3 domain. These data suggest that the cation channel–PKC association may require SH3 domain-mediated interactions to bring about modulation, promote membrane depolarization, and initiate prolonged changes in bag cell neuron excitability. In general, protein–protein interactions between ion channels and protein kinases may be a prominent mechanism underlying neuromodulation.
Assessing the Role of Calcium-Induced Calcium Release in Short-Term Presynaptic Plasticity at Excitatory Central Synapses
Authors: Carter Adam G. , Vogt Kaspar E. , Foster Kelly A. , Regehr Wade G.
Published: April 2018

Recent evidence suggests that internal calcium stores and calcium-induced calcium release (CICR) provide an important source of calcium that drives short-term presynaptic plasticity at central synapses. Here we tested for the involvement of CICR in short-term presynaptic plasticity at six excitatory synapses in acute rat hippocampal and cerebellar brain slices. Depletion of internal calcium stores with thapsigargin and prevention of CICR with ryanodine have no effect on paired-pulse facilitation, delayed release of neurotransmitter, or calcium-dependent recovery from depression. Fluorometric calcium measurements also show that these drugs have no effect on the residual calcium signal that underlies these forms of short-term presynaptic plasticity. Finally, although caffeine causes CICR in Purkinje cell bodies and dendrites, it does not elicit CICR in parallel fiber inputs to these cells. Taken together, these results indicate that for the excitatory synapses studied here, internal calcium stores and CICR do not contribute to short-term presynaptic plasticity on the milliseconds-to-seconds time scale. Instead, this plasticity is driven by the residual calcium signal arising from calcium entry through voltage-gated calcium channels.
Synaptic Potentials Mediated by α7 Nicotinic Acetylcholine Receptors in Supraoptic Nucleus
Authors: Hatton Glenn I. , Yang Qin Zhao
Published: April 2018

Brain slice preparations preserving projections from nearby forebrain cholinergic neurons to the supraoptic nucleus (SON) were used to study synaptic potentials mediated by nicotinic acetylcholine receptors (nAChRs) in the hypothalamus. Paired-pulse electrical stimulation in an area anterior to the SON that was rich in cholinergic cells confirmed the monosynaptic nature of the connections to putative oxytocin and vasopressin SON neurons. With ionotropic glutamate and GABAAtransmission blocked, this stimulation evoked fast, atropine-insensitive EPSPs that were sensitive to nAChR antagonists. Evoked EPSPs were blocked by methyllycaconitine and α-bungarotoxin, antagonists that are selective for nAChRs containing the α7 subunit, but not by dihydro-β-erythroidine at concentrations known to antagonize α4β2 nAChRs. Although anatomical evidence exists for postsynaptic α4β2 nAChRs in the SON, these results indicate that postsynaptic α7 nAChRs are primarily responsible for the cholinergically mediated EPSPs. Repetitive stimulation suggested partial desensitization of the receptors. With ionotropic glutamate transmission blocked, inhibition of AChE increased spontaneous EPSP frequency and amplitude, suggesting spontaneous ACh release. ACh, nicotine, and choline (a selective α7 nAChR agonist) were effective in evoking action potentials and repetitive firing with synaptic transmission blocked by low Ca2+, high Mg2+medium. These agonists were also effective in evoking the type of phasic bursts characteristic of vasopressin neurons, long thought to be completely dependent on activation of NMDA receptors (NMDARs). Because phasic bursting is Ca2+-dependent, the functional equivalence of α7 nAChR and NMDAR activation in this regard is likely attributable to their large Ca2+fluxing capacities. This is the first demonstration that synaptically released ACh results in fast, α7 nAChR-mediated EPSPs in hypothalamic neurons.
Activity- and Target-Dependent Regulation of Large-Conductance Ca2+-Activated K+Channels in Developing Chick Lumbar Motoneurons
Authors: Martin-Caraballo Miguel , Dryer Stuart E.
Published: April 2018

The functional expression of large-conductance (BK-type) Ca2+-activated K+(KCa) channels was examined in developing chick lumbar motoneurons (LMNs) between embryonic day 6 (E6) and E13 using patch-clamp recording techniques. The macroscopic KCacurrent of E13 LMNs is inhibited by iberiotoxin and resistant to apamin. The average macroscopic KCadensity was low before E8 and increased 3.3-fold by E11, with an additional 1.8-fold increase occurring by E13. BK-type KCachannels could not be detected in inside-out patches from E8 LMNs but were readily detected at E11. The density of voltage-activated Ca2+currents did not change between E8 and E11. Surgical ablation of target tissues at E5 caused a significant reduction in average KCadensity in LMNs measured at E11. Conversely, chronicin ovoadministration ofd-tubocurarine, which causes an increase in motoneuron branching on the surface of the muscle target tissue, evoked a 1.8-fold increase in average LMN KCadensity measured at E11. Electrical activity also contributed to developmental regulation of LMN KCadensity. A significant reduction in E11 KCadensity was found after chronicin ovotreatment with the neuronal nicotinic antagonist mecamylamine or the GABA receptor agonist muscimol, agents that reduce activation of LMNsin ovo. Moreover, 3 d exposure to depolarizing concentrations of external K+to LMNs cultured at E8 caused an increase in KCaexpression. Conversely, tetrodotoxin caused a decrease in KCaexpression in cultured E8 LMNs developing for 3 d in the presence of neurotrophic factors that promote neuronal survival in the absence of target tissues.
Peripheral Inflammation Sensitizes P2X Receptor-Mediated Responses in Rat Dorsal Root Ganglion Neurons
Authors: Xu Guang-Yin , Huang Li-Yen Mae
Published: April 2018

ATP-gated P2X receptors in nociceptive sensory neurons participate in transmission of pain signals from the periphery to the spinal cord. To determine the role of P2X receptors under injurious conditions, we examined ATP-evoked responses in dorsal root ganglion (DRG) neurons isolated from rats with peripheral inflammation, induced by injections of complete Freund's adjuvant (CFA) into the hindpaw. Application of ATP induced both fast- and slow-inactivating currents in control and inflamed neurons. CFA treatment had no effect on the affinity of ATP for its receptors or receptor phenotypes. On the other hand, inflammation caused a twofold to threefold increase in both ATP-activated currents, altered the voltage dependence of P2X receptors, and enhanced the expression of P2X2 and P2X3 receptors. The increase in ATP responses gave rise to large depolarizations that exceeded the threshold of action potentials in inflamed DRG neurons. Thus, P2X receptor upregulation could account for neuronal hypersensitivity and contribute to abnormal pain responses associated with inflammatory injuries. These results suggest that P2X receptors are useful targets for inflammatory pain therapy.
Jerky, a Protein Deficient in a Mouse Epilepsy Model, Is Associated with Translationally Inactive mRNA in Neurons
Authors: Liu Wencheng , Seto Jeremy , Donovan Gerald , Toth Miklos
Published: April 2018

Temporal lobe epilepsy (TLE) is a common seizure disorder, but the underlying molecular mechanisms are unknown. We reported previously that inactivation of thejerkygene in mice causes recurrent limbic seizures highly similar to TLE. Electrophysiological studies showed abnormal firing in hippocampal neurons in these mice, but it is not known how a deficiency in the Jerky protein leads to neuronal hyperexcitability. Here we show that Jerky is a brain-specific protein with a high expression level in neurons. Jerky binds mRNAs with high affinity, and it is a component of messenger ribonucleoprotein complexesin vivo. However, Jerky is not associated with ribosomes and actively translating mRNAs. These data suggest that Jerky may regulate mRNA use in neurons, and its deficiency could lead to perturbations in the regulated use of preexisting mRNAs.
Mice Deficient for Both Corticotropin-Releasing Factor Receptor 1 (CRFR1) and CRFR2 Have an Impaired Stress Response and Display Sexually Dichotomous Anxiety-Like Behavior
Authors: Bale Tracy L. , Picetti Roberto , Contarino Angelo , Koob George F. , Vale Wylie W. , Lee Kuo-Fen
Published: April 2018

Corticotropin-releasing factor (CRF) and its family of peptides are critical coordinators of homeostasis whose actions are mediated through their receptors, CRF receptor 1 (CRFR1) and CRFR2, found throughout the CNS and periphery. The phenotypes of mice deficient in either CRFR1 or CRFR2 demonstrate the critical role these receptors play. CRFR1-mutant mice have an impaired stress response and display decreased anxiety-like behavior, whereas CRFR2-mutant mice are hypersensitive to stress and display increased anxiety-like behavior. To further elucidate the roles of both CRF receptors and determine their interaction in behaviors, we have generated mice deficient in both CRFR1 and CRFR2. The behavioral phenotype of these mice demonstrates a novel role of the mother's genotype on development of pup anxiety. We have found that although the female double-mutant mice display anxiolytic-like behavior, the male double-mutant mice show significantly more anxiety-like behavior compared with the females. We have also determined that the dam's CRFR2 genotype affects the anxiety-like behavior of the male mice, such that a pup born to a heterozygous or mutant dam displays significantly more anxiety-like behavior regardless of that pup's genotype. Double-mutant mice also display an even greater impairment of their hypothalamic–pituitary–adrenal axis response to stress than that of the CRFR1-mutant mice. CRF mRNA levels are elevated in CRFR1- and double-mutant mice, and urocortin III and vasopressin mRNA levels are increased in CRFR2- and double-mutant mice. These results indicate that both CRFR1 and CRFR2 have critical roles in gene regulation and the maintenance of homeostasis in response to stress.
Short-Term Retrograde Inhibition of GABAergic Synaptic Currents in Rat Purkinje Cells Is Mediated by Endogenous Cannabinoids
Authors: Diana Marco A. , Levenes Carole , Mackie Ken , Marty Alain
Published: April 2018

Depolarization-induced suppression of inhibition (DSI) is a form of short-term plasticity of GABAergic synaptic transmission that is found in cerebellar Purkinje cells and hippocampal CA1 pyramidal cells. DSI involves the release of a calcium-dependent retrograde messenger by the somatodendritic compartment of the postsynaptic cell. Both glutamate and endogenous cannabinoids have been proposed as retrograde messenger.

Here we show that, in cerebellar parasagittal slices, type 1 cannabinoid receptors (CB1Rs) are expressed at high levels in axons of GABAergic interneurons and in presynaptic terminals onto Purkinje cells. Application of the cannabinoid antagonist AM-251 (500 nm) leads to the abolition of the DSI of evoked currents (eIPSCs) recorded in paired recordings and to a strong reduction of the DSI of TTX-insensitive miniature events (mIPSCs) recorded from Purkinje cells. Furthermore, the CB1R agonist WIN 55–212,2 (5 μm) induces a presynaptic inhibition of synaptic currents similar to that occurring during DSI, as well as an occlusion of DSI after stimulation of Purkinje cells. Moreover, WIN 55–212,2 reduces the calcium transients evoked in presumed presynaptic varicosities by short trains of action potentials.

Our results indicate that DSI is mediated by the activation of presynaptic CB1Rs and that an endogenous cannabinoid is a likely candidate retrograde messenger in this preparation. They further suggest that DSI involves distinct presynaptic modifications for eIPSCs and mIPSCs, including an inhibition of action potential-evoked calcium rises.
Zic2Controls Cerebellar Development in Cooperation withZic1
Authors: Aruga Jun , Inoue Takashi , Hoshino Jun , Mikoshiba Katsuhiko
Published: April 2018

MouseZicgenes encode zinc finger proteins and are expressed in the developing and mature CNS. Reduced expression ofZic2in mice results in spina bifida and holoprosencephaly. However, the disruption ofZic1, a strong homolog ofZic2that has an overlapping expression pattern, results in cerebellar malformation with no apparent abnormalities in the forebrain or in posterior neuropore closure. Here we revealed thatZic2andZic1cooperatively control cerebellar development by regulating neuronal differentiation. BothZic1andZic2are expressed in the precursor cells of the granule neuron and the neurons in cerebellar nuclei. Mice carrying one mutatedZic1allele together with one mutatedZic2allele (Zic1+/−Zic2+/kd) showed a marked cerebellar folial abnormality similar to, but distinct from that found in mice homozygous for theZic1mutation (Zic1−/−). TheZic1+/−Zic2+/kdcerebellum is missing a lobule in the anterior vermis and has a truncation of the most posterior lobule. Expression of transverse zonal markers is shifted anteriorly in the developing cerebellum, indicating that the anterior part of the cerebellum is poorly developed. Abnormalities in the developingZic1+/−Zic2+/kdcerebellum share the following features with those of theZic1−/−cerebellum: a preceding reduction of cell proliferation in the anterior external germinal layer, a reduction incyclin D1expression, and enhanced expression of the mitosis inhibitorsp27andp16, and enhancement ofWnt7aexpression. These results indicate thatZic1andZic2may have very similar functions in the regulation of cerebellar development.
Functional Redundancy of Ventral Spinal Locomotor Pathways
Authors: Loy David N. , Magnuson David S. K. , Zhang Y. Ping , Onifer Stephen M. , Mills Michael D. , Cao Qi-lin , Darnall Jessica B. , Fajardo Lily C. , Burke Darlene A. , Whittemore Scott R.
Published: April 2018

Identification of long tracts responsible for the initiation of spontaneous locomotion is critical for spinal cord injury (SCI) repair strategies. Pathways derived from the mesencephalic locomotor region and pontomedullary medial reticular formation responsible for fictive locomotion in decerebrate preparations project to the thoracolumbar levels of the spinal cord via reticulospinal axons in the ventrolateral funiculus (VLF). However, white matter regions critical for spontaneous over-ground locomotion remain unclear because cats, monkeys, and humans display varying degrees of locomotor recovery after ventral SCIs. We studied the contributions of myelinated tracts in the VLF and ventral columns (VC) to spontaneous over-ground locomotion in the adult rat using demyelinating lesions. Animals received ethidium bromide plus photon irradiation producing discrete demyelinating lesions sufficient to stop axonal conduction in the VLF, VC, VLF–VC, or complete ventral white matter (CV). Behavior [open-field Basso, Beattie, and Bresnahan (BBB) scores and grid walking] and transcranial magnetic motor-evoked potentials (tcMMEP) were studied at 1, 2, and 4 weeks after lesion. VLF lesions resulted in complete loss or severe attenuation of tcMMEPs, with mean BBB scores of 18.0, and no grid walking deficits. VC lesions produced behavior similar to VLF-lesioned animals but did not significantly affect tcMMEPs. VC–VLF and CV lesions resulted in complete loss of tcMMEP signals with mean BBB scores of 12.7 and 6.5, respectively. Our data support a diffuse arrangement of axons within the ventral white matter that may comprise a system of multiple descending pathways subserving spontaneous over-ground locomotion in the intact animal.
Oficios de salitre. As mulleres e os traballos do mar
Authors: Iglesias Villaverde Xiana , Abelleira Fontán María
Published: April 2018

Este artigo pretende contribuír a visibilizar unha historia, a das mulleres, que permaneceu oculta durante séculos e que en parte foi e segue a ser descoñecida. A través do relato construído en base a conversas con traballadoras do mar da zona de Pontevedra podemos coñecer como foron cambiando os oficios desde a súa infancia até hoxe en día; en que circunstancias e en que contexto tiveron que pelexar para defender o seu posto de traballo; como se foi regularizando a súa situación e que implicacións tiveron para elas.
O traballo das mulleres na LIX: o rural e o mar en tres obras pioneiras
Authors: Mociño González Isabel
Published: April 2018

Neste traballo analízase cómo se representou (ou silenciou) o traballo das mulleres no agro e no mar. Faise a través de, fundamentalmente, tres obras pioneiras que se publicaron dirixidas á infancia e xuventude: Memorias dun neno labrego (1961, 1968), de Xosé Neira Vilas; Mar adiante (1973), de María Victoria Moreno; e O segredo da Pedra Figueira (1985), de María Xosé Queizán. Son obras publicadas na fase de constitución do sistema literario que abriron vías ata o de entón inexploradas ou pouco tratadas e que serviron de modelo para creadores e creadoras posteriores. Considerámolas relevantes por confluír nelas tamén tradición e modernidade, ademais de amosaren de modos moi diversos o traballo das mulleres en diferentes ámbitos e dende diferentes perspectivas.
Mulleres diante. Rostros femininos e acción colectiva no rural galego
Authors: Cabana Iglesia Ana
Published: April 2018

Fronte á idea asentada da inexistencia de accións sociais colectivas de carácter reivindicativo no rural galego ata as últimas datas do franquismo e ós estereotipos de xénero do nacionalcatolicismo que relegaban á muller a un espazo privado definido pola submisión, o presente texto trata de resaltar a presenza de mulleres á cabeza de movementos de protesta nese período. E farémolo seguindo o fío condutor das reivindicacións en contra da Hermandad Sindical de Labradores y Ganaderos que materializaron as labregas do concello de Pontevedra nos anos cincuenta. Trataremos de interpretar as estratexias empregadas para manobrar dentro das circunstancias impostas por un réxime ditatorial así como escudriñar no universo simbólico ó que apelaban para arrogarse a representación das súas familias e comunidade nun momento de conflito aberto.
A lírica profana galego-portuguesa contada aos mozos, entre realidade e ficción
Authors: Vázquez García Tania
Published: April 2018

Neste traballo realizaremos un achegamento crítico no que pretendemos cuestionar a realidade literaria que se lle presenta ao alumnado sobre o tema, así como a visión parcial do corpus ao que se dá acollida nos manuais de distintas editoriais empregadas no sistema educativo galego.
Los silencios en el "Ciclo das sombras", de Agustín Fernández Paz
Authors: Carbajo Lago María
Published: April 2018

El presente artículo estudia los silencios que persisten en torno a los episodios transcurridos durante la Guerra Civil española a partir del denominado “Ciclo de las sombras” del escritor gallego Agustín Fernández Paz (1947-2016) en el seno de la Literatura Infantil y Juvenil. El corpus con el que se ha trabajado constituye una trilogía adecuada para analizar esta cuestión, pues las novelas se presentan como verdaderas reivindicaciones de la recuperación de la memoria de las víctimas del conflicto de 1936. Su estudio permite observar las consecuencias que han producido la guerra y la fuerte represión sufrida durante los años del franquismo en décadas posteriores. Precisamente, con el fin de evitar el desconocimiento de lo que es parte de la historia de todo un país, el autor crea estas tres obras para formar a las nuevas generaciones y homenajear a todos aquellos que fueron silenciados.
Teatro, Infancia y Escuela: reflexiones sobre el género dramático en la Literatura Infantil
Authors: G-Pedreira Rocío
Published: April 2018

Teatro e infancia mantienen una relación muy sólida y productiva desde que el público infantil se asentó como un posible destinatario específico de estas obras. El teatro infantil ha estado relacionado desde sus inicios con la institución escolar, puesto que ha destacado, especialmente, por su potencial como herramienta didáctica para la transmisión de conocimientos y valores. No obstante, al igual que para el conjunto de la literatura, el valor estético es su principal requisito, lo que parece dificultarse para los escritores de obras dirigidas a los más jóvenes por la presión social sobre lo que deben decir, enseñar o transmitir. En el artículo se realizará una aproximación al término teatro infantil aportando datos que permitan definirlo y determinar su alcance, su evolución en el territorio español y se defenderá la posibilidad de recepción del género no sólo como espectáculo, también como texto de lectura.
Temáticas transgénero na literatura infantil
Authors: Verdade da Madalena Emanuel
Published: April 2018

Este artigo esboça uma perspetiva da presença de temáticas transgénero na literatura infantil publicada em vários países e línguas, e procura, necessariamente de forma não exaustiva, identificar, contextualizar e analisar um conjunto representativo de livros para a primeira infância que incluem explicitamente o tema da transgeneridade, ou que o trabalham implicitamente a partir de um dos principais outputs da identidade de género – o vestuário –, naqueles a que chamamos “os livros dos vestidos”. Depois das primeiras considerações introdutórias, prossegue-se com a intersecção das temáticas transgénero na literatura em geral com a sua presença nos livros para crianças, traçando brevemente uma evolução histórica e descrevendo a sua importância para um primeiro movimento didático da transgeneridade. Na análise aos livros, além de distinguirmos o tratamento explícito ou implícito do tema, damos especial atenção ao tipo de marcas e de metáforas utilizadas para veicular a não-conformidade de género e a transição, procurando sempre considerar a qualidade das propostas e a sua adequação ao público-alvo ou aos objetivos ativistas dos autores.