bluuebunny/crossref_metadata_2025 huggingface dataset:
Estrogen-Induced Alteration of μ-Opioid Receptor Immunoreactivity in the Medial Preoptic Nucleus and Medial Amygdala
Authors: Eckersell Clair B. , Popper Paul , Micevych Paul E
Published: April 2018

The μ-opioid receptor (μ-OR), like most G-protein-coupled receptors, is rapidly internalized after agonist binding. Although opioid peptides induce internalizationin vivo, there are no studies that demonstrate μ-OR internalization in response to natural stimuli. In this study, we used laser-scanning microscopy to demonstrate that estrogen treatment induces the translocation of μ-OR immunoreactivity (μ-ORi) from the membrane to an internal location in steroid-sensitive cell groups of the limbic system and hypothalamus. Estrogen-induced internalization was prevented by the opioid antagonist naltrexone, suggesting that translocation was largely dependent on release of endogenous agonists. Estrogen treatment also altered the pattern of μ-ORi at the bright-field light microscopic level. In the absence of stimulation, the majority of immunoreactivity is diffuse, with few definable μ-OR+ cell bodies or processes. After stimulation, the density of distinct processes filled with μ-ORi was significantly increased. We interpreted the increase in the number of μ-OR+ processes as indicating increased levels of internalization. Using this increase in the density of μ-OR+ fibers, we showed that treatment of ovariectomized rats with estradiol benzoate induced a rapid and reversible increase in the number of fibers. Significant internalization was noted within 30 min and lasted for >24 hr after estrogen treatment in the medial preoptic nucleus, the principal part of the bed nucleus, and the posterodorsal medial amygdala. Naltrexone prevented the increase of μ-OR+ processes. These data imply that estrogen treatment stimulates the release of endogenous opioids that activate μ-OR in the limbic system and hypothalamus providing a “neurochemical signature” of steroid activation of these circuits.
Distinctive Morphological Features of a Subset of Cortical Neurons Grown in the Presence of Basal Forebrain NeuronsIn Vitro
Authors: Ha Dun H. , Robertson Richard T. , Weiss John H.
Published: April 2018

Basal forebrain cholinergic neurons (BFCNs) provide the major subcortical source of cholinergic input to cerebral cortex and play an important role in regulating cortical activity. The present study examined the ability of BFCNs to influence neocortical neuronal growth by examining effects of the presence of BFCNs on certain cortical neurons grown under the controlled conditions of dissociated cell culture. Initial experiments demonstrated distinctive morphological features of a population of neurons (labeled with SMI-32, a monoclonal antibody to nonphosphorylated neurofilament proteins that labels pyramidal neuronsin vivo) in cocultures containing basal forebrain (BF) and cortical cells. These neurons (large neurons immunoreactive for SMI-32 [SMI-32(+) neurons]) were characterized as having extensive axons, greater soma size, and more dendritic growth than did most SMI-32(+) neurons in the cultures. Staining for SMI-32 in cocultures in which the cortical neurons were labeled with a fluorescent marker before adding the BF cells indicated that virtually all large SMI-32(+) neurons were of cortical origin. Eliminating BFCNs with the selective cholinergic immunotoxin 192 IgG–saporin resulted in a >80% decrease in the number of large SMI-32(+) neurons, although causing little damage to other cells in the treated cultures; this suggests that survival or maintenance of large SMI-32(+) neurons may depend on ongoing trophic support from BFCNs. Thus, present findings suggest that BFCNs may provide powerful growth- and/or survival-enhancing signals to a subset of cortical neurons.
Seizure-Induced Neuronal Injury: Vulnerability to Febrile Seizures in an Immature Rat Model
Authors: Toth Zsolt , Yan Xiao-Xin , Haftoglou Suzie , Ribak Charles E. , Baram Tallie Z.
Published: April 2018

Febrile seizures are the most common seizure type in young children. Whether they induce death of hippocampal and amygdala neurons and consequent limbic (temporal lobe) epilepsy has remained controversial, with conflicting data from prospective and retrospective studies. Using an appropriate-age rat model of febrile seizures, we investigated the acute and chronic effects of hyperthermic seizures on neuronal integrity and survival in the hippocampus and amygdala via molecular and neuroanatomical methods. Hyperthermic seizures–but not hyperthermia alone–resulted in numerous argyrophilic neurons in discrete regions of the limbic system; within 24 hr of seizures, a significant proportion of neurons in the central nucleus of the amygdala and in the hippocampal CA3 and CA1 pyramidal cell layer were affected. These physicochemical alterations of hippocampal and amygdala neurons persisted for at least 2 weeks but were not accompanied by significant DNA fragmentation, as determined byin situend labeling. By 4 weeks after the seizures, no significant neuronal dropout in these regions was evident. In conclusion, in the immature rat model, hyperthermic seizures lead to profound, yet primarily transient alterations in neuronal structure.
Induction of a Specific Olfactory Memory Leads to a Long-Lasting Activation of Protein Kinase C in the Antennal Lobe of the Honeybee
Authors: Grünbaum Lore , Müller Uli
Published: April 2018

In this study we investigated the role of protein kinase C (PKC) in associative learning ofApis mellifera. Changes in PKC activity induced by olfactory conditioning were measured in the antennal lobes, a brain structure involved in associative learning. Multiple conditioning trials inducing a memory different from that induced by a single conditioning trial specifically cause an increase in PKC activity. This increase begins 1 hr after conditioning, lasts up to 3 d, and is attributable to an increased level of constitutive PKC. The increased level of constitutive PKC consists of an early proteolysis-dependent phase and a late phase that requires RNA and protein synthesis. Inhibition of the pathways resulting in constitutive PKC selectively impairs distinct phases of multiple-trial induced memory. The inhibition of the proteolytic mechanism has an instant effect on an early phase of multiple-trial induced memory but does not affect acquisition and the late phase of memory. Blocking of the transient PKC activation during conditioning does not affect the induction of memory formation. Thus, the constitutive PKC in the antennal lobe seems to contribute to the early phase of memory that is induced by multiple-trial conditioning.
Activation of Coeruleospinal Noradrenergic Inhibitory Controls during Withdrawal from Morphine in the Rat
Authors: Rohde Dana S. , Basbaum Allan I.
Published: April 2018

We previously reported that withdrawal from morphine induces the expression of Fos, a marker of neuronal activity, in spinal cord neurons, particularly in laminae I and II of the superficial dorsal horn, and that the magnitude of Fos expression is increased in rats with a midthoracic spinal transection. We suggested that loss of withdrawal-associated increases in descending inhibitory controls that arise in the brainstem underlie the increased Fos expression after spinal transection. Here, we addressed the origin of the supraspinal inhibition. We injected rats intracerebroventricularly with saline or anti-dopamine-β-hydroxylase–saporin, a toxin that destroys noradrenergic neurons of the locus coeruleus. Eleven days later, we implanted rats with morphine or placebo pellets, and after 4 d, we precipitated withdrawal with naltrexone. One hour later, the rats were killed, their brains and spinal cords were removed, and transverse sections of the brains and spinal cords were immunoreacted with an antibody to Fos.

In placebo-pelleted rats, the toxin injection did not alter behavior and did not induce expression of the Fos protein. However, compared with saline-injected withdrawing rats, the toxin-treated rats that underwent withdrawal demonstrated an intense withdrawal behavior rarely seen in the absence of toxin, namely forepaw fluttering. The rats also had significantly increased Fos-like immunoreactivity in all laminae of the cervical cord and in laminae I and II and the ventral horn of the lumbar cord. No differences were recorded in the sacral cord. We conclude that the effects of spinal transection in rats that withdraw from morphine in part reflect a loss of coeruleospinal noradrenergic inhibitory controls.
Perceptual Correlates of Changes in Cortical Representation of Fingers in Blind Multifinger Braille Readers
Authors: Sterr Annette , Müller Matthias M. , Elbert Thomas , Rockstroh Brigitte , Pantev Christo , Taub Edward
Published: April 2018

The mature mammalian nervous system alters its functional organization in a use-dependent manner. Enhanced stimulation of a body part enlarges its cortical representational zones and may change its topographic order. Little is known about the perceptual and behavioral relevance of these plastic alterations in cortical organization. We used blind Braille readers who use several fingers on each hand and who do so for many hours each day as a model to investigate this issue. Magnetic source imaging indicated that the cortical somatosensory representation of the fingers was frequently topographically disordered in these subjects; in addition, they frequently misperceived which of these fingers was being touched by a light tactile stimulus. In contrast, neither the disordered representation nor mislocalizations were observed in sighted controls. Blind non-teacher Braille readers who used only one finger for reading were not significantly different from the sighted controls. Thus, use-dependent cortical reorganization can be associated with functionally relevant changes in the perceptual and behavioral capacities of the individual.
Evidence for Metabotropic Glutamate Receptor Activation in the Induction of Depolarization-Induced Suppression of Inhibition in Hippocampal CA1
Authors: Morishita Wade , Kirov Sergei A. , Alger Bradley E.
Published: April 2018

Depolarization-induced suppression of inhibition (DSI) is a transient reduction of GABAAreceptor-mediated IPSCs that is mediated by a retrograde signal from principal cells to interneurons. Using whole-cell recordings, we tested the hypothesis that mGluRs are involved in the DSI process in hippocampal CA1, as has been proposed for cerebellar DSI. Group II mGluR agonists failed to affect either evoked monosynaptic IPSCs or DSI, and forskolin, which blocks cerebellar DSI, did not affect CA1 DSI. Group I and group III mGluR agonists reduced IPSCs, but only group I agonists occluded DSI. (S)-MCPG blocked (1S,3R)-ACPD-induced IPSC suppression and markedly reduced DSI, whereas group III antagonists had no effect on DSI. Many other similarities between DSI and the (1S,3R)-ACPD-induced suppression of IPSCs also were found. Our data suggest that a glutamate-like substance released from pyramidal cells could mediate CA1 DSI by reducing GABA release from interneurons via the activation of group I mGluRs.
Endogenous Regulation of Serotonin Release in the Hamster Suprachiasmatic Nucleus
Authors: Dudley Thomas E. , DiNardo Lisa A. , Glass J. David
Published: April 2018

Serotonin (5-HT) has been strongly implicated in the regulation of the mammalian circadian clock located in the suprachiasmatic nuclei (SCN). However, little is known of the pattern of neuronal 5-HT release in the SCN or of the factors involved in regulating its release. Usingin vivomicrodialysis, we demonstrated the existence of a daily rhythm in the output of 5-HT in the SCN of freely behaving hamsters. This rhythm was characterized by a sharp increase in release from a nadir during late midday to peak levels at the light/dark transition. Output declined to basal levels throughout the remainder of the night. A similar pattern also was evident under constant darkness, with increased 5-HT output occurring at the onset of subjective night. Locomotor activity induced by exposure to a novel running wheel had a pronounced phase-dependent effect on 5-HT release in the SCN, with stimulation during the light phase and suppression during the late dark phase. Systemic application of the somatodendritic 5-HT1Aagonist BMY 7378 had a significantly greater suppressive effect on 5-HT release in the SCN during the late dark phase compared with mid light phase, indicating that a variation in raphe autoreceptor response may underlie the time-dependent effects of wheel running on 5-HT release. Collectively, these results show that the daily rhythm in output of 5-HT in the SCN is generated endogenously, and that behavioral state can strongly influence serotonergic activity in the circadian clock in a phase-dependent manner.
Cyclosporin A, But Not FK 506, Protects Mitochondria and Neurons against Hypoglycemic Damage and Implicates the Mitochondrial Permeability Transition in Cell Death
Authors: Friberg Hans , Ferrand-Drake Michel , Bengtsson Finn , Halestrap Andrew P. , Wieloch Tadeusz
Published: April 2018

Induction of the mitochondrial permeability transition (MPT) has been implicated in cellular apoptosis and in ischemia–reperfusion injury. During MPT, a channel in the inner mitochondrial membrane, the mitochondrial megachannel, opens and causes isolated mitochondria to swell. MPT and mitochondrial swelling is inhibited by cyclosporin A (CsA), which may also inhibit apoptosis in some cells.

Treatment with CsA (50 mg/kg, i.v.) showed a robust reduction of brain damage when administered 30 min before insulin-induced hypoglycemic isoelectricity of 30 min duration. Ultrastructural examination of the dentate gyrus revealed a marked swelling of dendrites and mitochondria during the hypoglycemic insult. In CsA-treated animals, mitochondria resumed a normal and contracted appearance during and after the hypoglycemic insult. Treatment with FK 506 (2 mg/kg, i.v.), a compound with immunosuppressive action similar to that of CsA, was not protective. Studies on the swelling kinetics of isolated mitochondria from the hippocampus showed that CsA, but not FK 506, inhibits calcium ion-induced MPT.

We conclude that CsA treatment during hypoglycemic coma inhibits the MPT and reduces damage and that mitochondria and the MPT are likely to be involved in the development of hypoglycemic brain damage in the rat.
Comparison of Hippocampal Dendritic Spines in Culture and in Brain
Authors: Boyer Christopher , Schikorski Thomas , Stevens Charles F.
Published: April 2018

We have quantified hippocampal spine structure at the light and ultrastructural levels in cell cultures ∼1- 3 weeks old and in the brains of rodents 5 and 21 d old. The number of spines bearing synapses increases with age in cultures and in brain, but the structures are similar in both. In culture, about half of the synapses are formed on spines and the remainder are formed on dendritic shafts. In the 5-d-old brain, about half of the synapses occur on dendritic shafts, by 3 weeks of age only ∼20% of synapses are found on dendritic shafts, and in the adult shaft synapses are very rare.
A Complex Program of Striatal Gene Expression Induced by Dopaminergic Stimulation
Authors: Berke Joshua D. , Paletzki Ronald F. , Aronson Gabriel J. , Hyman Steven E. , Gerfen Charles R.
Published: April 2018

Dopamine acting in the striatum is necessary for normal movement and motivation. Drugs that change striatal dopamine neurotransmission can have long-term effects on striatal physiology and behavior; these effects are thought to involve alterations in gene expression. Using the 6-hydroxydopamine lesion model of Parkinson’s disease and differential display PCR, we have identified a set of more than 30 genes whose expression rapidly increases in response to stimulation of striatal dopamine D1receptors. The induced mRNAs include both novel and previously described genes, with diverse time courses of expression. Some genes are expressed at near-maximal levels within 30 min, whereas others show no substantial induction until 2 hr or more after stimulation. Some of the induced genes, such as CREM, CHOP, and MAP kinase phosphatase-1, may be components of a homeostatic response to excessive stimulation. Others may be part of a genetic program involved in cellular and synaptic plasticity. A very similar set of genes is induced in unlesioned animals by administration of the psychostimulant cocaine or the antipsychotic eticlopride, although in distinct striatal cell populations. In contrast to some previously described early genes, most of the novel genes are not induced in cortex by apomorphine, indicating specificity of induction. Thus we have identified novel components of a complex, coordinated genetic program that is induced in striatal cells in response to various dopaminergic manipulations.
Hypothalamic Neurons Preferentially Respond to Female Nest Coo Stimulation: Demonstration of Direct Acoustic Stimulation of Luteinizing Hormone Release
Authors: Cheng Mei-Fang , Peng Jing Pian , Johnson Patricia
Published: April 2018

Avian vocalizations are generally understood to play a pivotal role in reproductive functions. The role of the hypothalamus in gonadotropin release in higher vertebrates including birds is well established. To date, however, a direct linkage between the neuronal processing of vocal input and the contingent luteinizing hormone (LH) response has not been demonstrated. In this study, using female ring doves, we recorded neuronal activity from hypothalamic nuclei that, as we have shown previously, receive acoustic inputs from the auditory thalamic relay. Concurrently with recording single-unit responses to stimulation with species-specific coo vocalizations, we sampled LH levels in blood from the pituitary veins. LH concentration in the plasma was significantly elevated in birds hearing species-typical coos but not in birds exposed to experimentally altered coos or white noise or in birds that received no vocal stimulation. We found two types of neurons in the preoptic and anterior hypothalamus that selectively responded to the female nest coo: excitatory units and inhibitory units. Among the excitatory neurons are units characterized by two bursts separated by a period of slow spiking or complete silence, in a pattern approximately corresponding temporally to the two-note coo. We designate them as female-nest-coo-specific units. Most neurons in the posterior hypothalamus were nonselective in their response. Female nest coo and male nest coo stimulation evoked an equal magnitude of discharge changes from responsive units in the preoptic-anterior hypothalamic area. We found, however, that the LH increment was three times greater for birds hearing female nest coos than for birds hearing male nest coos. These observations suggest that feature-detecting neurons such as the female-nest-coo-specific units are involved in gonadotropin-releasing hormone output. The present findings are consistent with the well established behavioral evidence that female nest coos mediate ovarian growth.
Formation of the Nicotinic Acetylcholine Receptor Binding Sites
Authors: Green William N. , Wanamaker Christian P.
Published: April 2018

Nicotinic acetylcholine receptors (AChRs) are activated by ACh binding to two sites located on different α subunits. The two α subunits, αγand αδ, are distinguished by their interface with γ and δ subunits. We have characterized the formation of the ACh binding sites and found, contrary to the current model, that the sites form at different times and in a set order. The first site forms on αγsubunits during the process of subunit assembly. Our data are consistent with the appearance of this site on αβγδ subunit tetramers soon after the site for the competitive antagonist α-bungarotoxin has formed and δ subunits have assembled with αβγ trimers. The second site is located on αδsubunits and forms after AChR subunits have assembled into α2βγδ pentamers. By determining the order in which the ACh binding sites form, we have also identified the sites in which the δ and second α subunits associate during subunit assembly.
Neurite Growth Patterns Leading to Functional Synapses in an Identified Embryonic Neuron
Authors: Reese David , Drapeau Pierre
Published: April 2018

We explored the relationship between neurite outgrowth and the onset of synaptic activity in the central neuropil of the leech embryoin vivo. To follow changes in early morphology and the onset of synaptic activity in the same identified neuron, we obtained whole-cell patch-clamp recordings and fluorescent dye fills from dorsal pressure-sensitive (P) cells, the first neurons that could be reliably identified in the early embryo. We followed the development of the P cell from the first extension of neurites to the elaboration of an adult-like arbor. After the growth of primary neurites, we observed a profuse outgrowth of transient neurites within the neuropil. Retraction of the transient neurites left the primary branches studded with spurs. After a dormant period, stable secondary branches grew apparently from the spurs and became tipped with terminals. At this time, neurites of the Retzius (R) cell, a known presynaptic partner in the adult, were observed to apparently contact the terminals. Although voltage-dependent currents were seen in the P cell at the earliest stage, spontaneous synaptic activity was only observed when terminals had formed. Spontaneous release was observed before evoked release could be detected from the R cell. Our results suggest that transient neurites are formed during an exploratory phase of development, whereas the more precisely timed outgrowth of stable neurites from the spurs signals functional differentiation during synaptogenesis. Because spurs have also been observed in neurons of the mammalian brain, they may constitute a primordial synaptic organizer.
Experimental Brain Injury Induces Regionally Distinct Apoptosis during the Acute and Delayed Post-Traumatic Period
Authors: Conti Alana C. , Raghupathi Ramesh , Trojanowski John Q. , McIntosh Tracy K.
Published: April 2018

The temporal pattern of apoptosis in the adult rat brain after lateral fluid-percussion (FP) brain injury was characterized using terminal deoxynucleotidyl-transferase-mediated biotin-dUTP nick end labeling (TUNEL) histochemistry and agarose gel electrophoresis. Male Sprague Dawley rats were subjected to brain injury and killed for histological analysis at intervals from 12 hr to 2 months after injury (n= 3/time point). Sham (uninjured) controls were subjected to anesthesia with (n= 3) or without (n= 3) surgery. Apoptotic TUNEL-positive cells were defined using stringent morphological criteria including nuclear shrinkage and fragmentation and condensation of chromatin and cytoplasm. Double-labeled immunocytochemistry was performed to identify TUNEL-positive neurons (anti-neurofilament monoclonal antibody RM044), astrocytes (anti-glial fibrillary acidic protein polyclonal antibody), and oligodendrocytes (anti-cyclic nucleotide phosphohydrolase polyclonal antibody). Compared with that seen with sham controls, in the injured cortex, significant apoptosis occurred at 24 hr (65 ± 19 cells;p< 0.05) with a second, more pronounced response at 1 week after injury (91 ± 24 cells;p< 0.05). The number of apoptotic cells in the white matter was increased as early as 12 hr after injury and peaked by 1 week (33 ± 6 cells;p< 0.05). An increase in apoptotic cells was observed in the hippocampus at 48 hr (13 ± 8), whereas in the thalamus, the apoptotic response was delayed, peaking at 2 weeks after injury (151 ± 71 cells;p< 0.05). By 2 months, the number of apoptotic cells in most regions had returned to uninjured levels. At 24 hr after injury, TUNEL-labeled neurons and oligodendrocytes were localized primarily to injured cortex. By 1 week after injury, populations of TUNEL-labeled astrocytes and oligodendrocytes were present in the injured cortex, while double-labeled neurons were present predominantly in injured cortex and thalamus, with a few scattered in the hippocampus. DNA agarose gels confirmed morphological identification of apoptosis. These data suggest that the apoptotic response to trauma is regionally distinct and may be involved in both acute and delayed patterns of cell death.
Tau Cleavage and Dephosphorylation in Cerebellar Granule Neurons Undergoing Apoptosis
Authors: Canu Nadia , Dus Laura , Barbato Christian , Ciotti Maria T. , Brancolini Claudio , Rinaldi Anna M. , Novak Michal , Cattaneo Antonino , Bradbury Andrew , Calissano Pietro
Published: April 2018

Cerebellar granule cells undergo apoptosis in culture after deprivation of potassium and serum. During this process we found that tau, a neuronal microtubule-associated protein that plays a key role in the maintenance of neuronal architecture, and the pathology of which correlates with intellectual decline in Alzheimer’s disease, is cleaved. The final product of this cleavage is a soluble dephosphorylated tau fragment of 17 kDa that is unable to associate with microtubules and accumulates in the perikarya of dying cells. The appearance of this 17 kDa fragment is inhibited by both caspase and calpain inhibitors, suggesting that tau is anin vivosubstrate for both of these proteases during apoptosis. Tau cleavage is correlated with disruption of the microtubule network, and experiments with colchicine and taxol show that this is likely to be a cause and not a consequence of tau cleavage.

These data indicate that tau cleavage and change in phosphorylation are important early factors in the failure of the microtubule network that occurs during neuronal apoptosis. Furthermore, this study introduces new insights into the mechanism(s) that generate the truncated forms of tau present in Alzheimer’s disease.
Nicotinic Stimulation Produces Multiple Forms of Increased Glutamatergic Synaptic Transmission
Authors: Radcliffe Kristofer A. , Dani John A.
Published: April 2018

Synaptic modulation and long-term synaptic changes are thought to be the cellular correlates for learning and memory (Madison et al., 1991; Aiba et al., 1994; Goda and Stevens, 1996). The hippocampus is a center for learning and memory that receives abundant cholinergic innervation and has a high density of nicotinic acetylcholine receptors (nAChRs) (Wada et al., 1989; Woolf, 1991). We report that strong, brief stimulation of nAChRs enhanced hippocampal glutamatergic synaptic transmission on two independent time scales and altered the relationship between consecutively evoked synaptic currents. The nicotinic synaptic enhancement required extracellular calcium and was produced by the activation of presynaptic α7-containing nAChRs. Although one form of glutamatergic enhancement lasted only for seconds, another form lasted for minutes after the nicotinic stimulation had ceased and the nicotinic agonist had been washed away. The synaptic enhancement lasting minutes suggests that nAChR activity can initiate calcium-dependent mechanisms that are known to induce glutamatergic synaptic plasticity. The results with evoked synaptic currents showed that nAChR activity can alter the relationship between the incoming presynaptic activity and outgoing postsynaptic signaling along glutamatergic fibers. Thus, the same information arriving along the same glutamatergic afferents will be processed differently when properly timed nicotinic activity converges onto the glutamatergic presynaptic terminals. Influencing information processing at glutamatergic synapses may be one way in which nicotinic cholinergic activity influences cognitive processes. Disruption of these nicotinic cholinergic mechanisms may contribute to the deficits associated with the degeneration of cholinergic functions during Alzheimer’s disease.
Functional Redundancy of FMRFamide-Related Peptides at theDrosophilaLarval Neuromuscular Junction
Authors: Hewes Randall S. , Snowdeal Eric C , Saitoe Minoru , Taghert Paul H.
Published: April 2018

TheDrosophila FMRFamidegene encodes multiple FMRFamide-related peptides. These peptides are expressed by neurosecretory cells and may be released into the blood to act as neurohormones. We analyzed the effects of eight of these peptides on nerve-stimulated contraction (twitch tension) ofDrosophilalarval body-wall muscles. Seven of the peptides strongly enhanced twitch tension, and one of the peptides was inactive. Their targets were distributed widely throughout the somatic musculature. The effects of one peptide, DPKQDFMRFamide, were unchanged after the onset of metamorphosis. The seven active peptides showed similar dose–response curves. Each had a threshold concentration near 1 nm, and the EC50for each peptide was ∼40 nm. At concentrations <0.1 μm, the responses to each of the seven excitatory peptides followed a time course that matched the fluctuations of the peptide concentration in the bath. At higher concentrations, twitch tension remained elevated for 5–10 min or more after wash-out of the peptide. When the peptides were presented as mixtures predicted by their stoichiometric ratios in the dFMRFamide propeptide, the effects were additive, and there were no detectable higher-order interactions among them. One peptide was tested and found to enhance synaptic transmission. At 0.1 μm, DPKQDFMRFamide increased the amplitude of the excitatory junctional current to 151% of baseline within 3 min. Together, these results indicate that the products of theDrosophila FMRFamidegene function as neurohormones to modulate the strength of contraction at the larval neuromuscular junction. In this role these seven peptides appear to be functionally redundant.
Intracellular Calcium and Cell Death during Ischemia in Neonatal Rat White Matter AstrocytesIn Situ
Authors: Fern Robert
Published: April 2018

The major pathological correlate of cerebral palsy is ischemic injury of CNS white matter. Histological studies show early injury of glial cells and axons. To investigate glial cell injury, I monitored intracellular Ca2+and cell viability in fura-2-loaded neonatal rat white matter glial cells during ischemia. Fura-2 fixation combined with immunohistochemistry revealed that fura-2-loaded cells were GFAP+/O4−and were therefore a population of neonatal white matter astrocytes.

Significant ischemic Ca2+influx was found, mediated by both L- and T-type voltage-gated Ca2+channels. Ca2+influx via T-type channels was the most important factor during the initial stage of ischemia and was associated with significant cell death within 10–20 min of the onset of ischemia. The Na+–Ca2+exchanger acted to remove cytoplasmic Ca2+throughout the ischemic and recovery periods. Neither the release of Ca2+from intracellular stores nor influx via glutamate-gated channels contributed to the rise in intracellular Ca2+during ischemia. Ischemic cell death was reduced significantly by removing extracellular Ca2+or by blocking voltage-gated Ca2+channels. The exclusively voltage-gated Ca2+channel nature of the Ca2+influx, the role played by T-type Ca2+channels, the protective effect of the Na+–Ca2+exchanger, and the lack of significant Ca2+release from intracellular stores are features of ischemia that have not been reported in other CNS cell types.
Neurotrophins Induce Formation of Functional Excitatory and Inhibitory Synapses between Cultured Hippocampal Neurons
Authors: Vicario-Abejón Carlos , Collin Carlos , McKay Ronald D. G. , Segal Menahem
Published: April 2018

Cell cultures were used to analyze the role of brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) in the development of synaptic transmission. Neurons obtained from embryonic day 18 (E18) rat hippocampus and cultured for 2 weeks exhibited extensive spontaneous synaptic activity. By comparison, neurons obtained from E16 hippocampus expressed very low levels of spontaneous or evoked synaptic activity. Neurotrophin treatment produced a sevenfold increase in the number of functional synaptic connections in the E16 cultures. BDNF induced formation of both excitatory and inhibitory synapses, whereas NT-3 induced formation of only excitatory synapses. These effects were independent of serum or the age of the glia bed used for the culture. They were not accompanied by significant changes in synaptic-vesicle-associated proteins or glutamate receptors. Treatment of the cultures with the neurotrophins for 3 d was sufficient to establish the maximal level of functional synapses. During this period, neurotrophins did not affect the viability or the morphology of the excitatory neurons, although they did produce an increase in the number and length of dendrites of the GABAergic neurons. Remarkably, only BDNF caused an increase in the number of axonal branches and in the total length of the axons of the GABAergic neurons. These results support a unique and differential role for neurotrophins in the formation of excitatory and inhibitory synapses in the developing hippocampus.
Sensory Processing in the Pallium of a Mormyrid Fish
Authors: Prechtl James C. , von der Emde Gerhard , Wolfart Jakob , Karamürsel Saçit , Akoev George N. , Andrianov Yuri N. , Bullock Theodore H.
Published: April 2018

To investigate the functional organization of higher brain levels in fish we test the hypothesis that the dorsal gray mantle of the telencephalon of a mormyrid fish has discrete receptive areas for several sensory modalities. Multiunit and compound field potentials evoked by auditory, visual, electrosensory, and water displacement stimuli in this weakly electric fish are recorded with multiple semimicroelectrodes placed in many tracks and depths in or near telencephalic area dorsalis pars medialis (Dm).

Most responsive loci are unimodal; some respond to two or more modalities. Each modality dominates a circumscribed area, chiefly separate. Auditory and electrical responses cluster in the dorsal 500 μm of rostral and caudolateral Dm, respectively. Two auditory subdivisions underline specialization of this sense. Mechanoreception occupies a caudal area overlapping electroreception but centered 500 μm deeper. Visual responses scatter widely through ventral areas.

Auditory, electrosensory, and mechanosensory responses are dominated by a negative wave within the first 50 msec, followed by 15–55 Hz oscillations and a slow positive wave with multiunit spikes lasting from 200 to 500 msec. Stimuli can induce shifts in coherence of certain frequency bands between neighboring loci. Every electric organ discharge command is followed within 3 msec by a large, mainly negative but generally biphasic, widespread corollary discharge. At certain loci large, slow (“δF”) waves usually precede transient shifts in electric organ discharge rate. Sensory-evoked potentials in this fish pallium may be more segregated than in elasmobranchs and anurans and have some surprising similarities to those in mammals.
A Protein Kinase, PKN, Accumulates in Alzheimer Neurofibrillary Tangles and Associated Endoplasmic Reticulum-Derived Vesicles and Phosphorylates Tau Protein
Authors: Kawamata Toshio , Taniguchi Taizo , Mukai Hideyuki , Kitagawa Michinori , Hashimoto Takeshi , Maeda Kiyoshi , Ono Yoshitaka , Tanaka Chikako
Published: April 2018

A possible role for a protein kinase, PKN, a fatty acid-activated serine/threonine kinase with a catalytic domain homologous to the protein kinase C family and a direct target for Rho, was investigated in the pathology of Alzheimer’s disease (AD) using a sensitive immunocytochemistry on postmortem human brain tissues and a kinase assay for human tau protein. The present study provides evidences by light, electron, and confocal laser microscopy that in control human brains, PKN is enriched in neurons, where the kinase is concentrated in a subset of endoplasmic reticulum (ER) and ER-derived vesicles localized to the apical compartment of juxtanuclear cytoplasm, as well as late endosomes, multivesicular bodies, Golgi bodies, secretary vesicles, and nuclei. In AD-affected neurons, PKN was redistributed to the cortical cytoplasm and neurites and was closely associated with neurofibrillary tangles (NFTs) and their major constituent, abnormally modified tau. PKN was also found in degenerative neurites within senile plaques. In addition, we report that human tau protein is directly phosphorylated by PKN bothin vitroandin vivo. Thus, our results suggest a specific role for PKN in NFT formation and neurodegeneration in AD damaged neurons.
Where and When to Pay Attention: The Neural Systems for Directing Attention to Spatial Locations and to Time Intervals as Revealed by Both PET and fMRI
Authors: Coull Jennifer T. , Nobre Anna C.
Published: April 2018

Although attention is distributed across time as well as space, the temporal allocation of attention has been less well researched than its spatial counterpart. A temporal analog of the covert spatial orientation task [Posner MI, Snyder CRR, Davidson BJ (1980) Attention and the detection of signals. J Exp Psychol Gen 109:160–174] was developed to compare the neural systems involved in directing attention to spatial locations versus time intervals. We asked whether there exists a general system for allocating attentional resources, independent of stimulus dimension, or whether functionally specialized brain regions are recruited for directing attention toward spatial versus temporal aspects of the environment. We measured brain activity in seven healthy volunteers by using positron emission tomography (PET) and in eight healthy volunteers by using functional magnetic resonance imaging (fMRI). The task manipulated cued attention to spatial locations (S) and temporal intervals (T) in a factorial design. Symbolic central cues oriented subjects toward S only (left or right), toward T only (300 msec or 1500 msec), toward both S and T simultaneously, or provided no information regarding S or T. Subjects also were scanned during a resting baseline condition. Behavioral data showed benefits and costs for performance during temporal attention similar to those established for spatial attention. Brain-imaging data revealed a partial overlap between neural systems involved in the performance of spatial versus temporal orientation of attention tasks. Additionally, hemispheric asymmetries revealed preferential right and left parietal activation for spatial and temporal attention, respectively. Parietal cortex was activated bilaterally by attending to both dimensions simultaneously. This is the first direct comparison of the neural correlates of attending to spatial versus temporal cues.
Relationship between Fos Production and Classical Fear Conditioning: Effects of Novelty, Latent Inhibition, and Unconditioned Stimulus Preexposure
Authors: Radulovic Jelena , Kammermeier Jens , Spiess Joachim
Published: April 2018

The relationship between FOS production in the sensory cortex and limbic system and the ability of C57BL/6N mice to acquire context- and tone-dependent freezing were investigated after fear conditioning, which was achieved by exposure of mice to context only or context and tone (10 kHz, 75 dB) as conditioned stimuli (Cs) paired with an electric footshock (0.7 mA, constant) as unconditioned stimulus (Us). The effect of preexposure to Cs or Cs paired with Us on FOS production and learning was also tested. It was demonstrated that high simultaneous FOS production in the parietal cortex, hippocampus, and amygdala paralleled the ability of mice to acquire strong freezing responses to novel Cs. After contextual preexposure (latent inhibition), FOS production could be elicited in the central amygdala only by shock and in the basolateral amygdala only by tone. Under these conditions, the ability of mice to acquire contextual freezing was almost abolished, whereas tone-dependent freezing was reduced. Lacking FOS production in the central amygdala after preexposure to context followed by shock (Us preexposure effect) paralleled the inability of mice to acquire tone-dependent freezing, although the tone elicited FOS production in the basolateral amygdala. On the basis of these findings it was concluded that synchronous Cs- and Us-induced FOS production in several defined forebrain areas was accompanied with associative learning of novel stimuli, and that a subsequent low level of FOS production might have been responsible or indicative for delayed conditioning to those stimuli.
Tyrosine Hydroxylase Expression in Primary Cultures of Olfactory Bulb: Role of L-Type Calcium Channels
Authors: Cigola Elena , Volpe Bruce T. , Lee Jong Wha , Franzen Linda , Baker Harriet
Published: April 2018

Sensory activity mediates regulation of tyrosine hydroxylase (TH), the first enzyme in the dopamine biosynthetic pathway, in the rodent olfactory bulb. The current studies established for the first time primary cultures of neonatal mouse olfactory bulb expressing TH and tested whether L-type calcium channels mediate the activity-dependent regulation of the dopamine phenotype. After 1 din vitro(DIV), a small population of TH-immunostained neurons that lacked extensive processes could be demonstrated. After an additional 2 DIV in serum-free medium, the number of TH neurons had doubled, and they exhibited long interdigitating processes. Membrane depolarization for 48 hr with 50 mmKCl produced a further 2.4-fold increase in the number of TH-immunoreactive neurons compared with control cultures. Increased TH neuron number required at least 36 hr of exposure to KCl. Forskolin, which increases intracellular cAMP levels, induced a 1.5- to 1.6-fold increase in the number of TH-immunostained neurons. Combined treatment with KCl and forskolin was not additive. Nifedipine, an L-type calcium channel blocker, completely prevented the depolarization-mediated increase in TH expression but did not block the response to forskolin. Treatment with Bay K8644, an L-type calcium channel agonist, also significantly increased the number of TH-expressing neurons. Depolarization also induced alterations in neuritic outgrowth, resulting in a stellate versus an elongate morphology that, in contrast, was not prevented by nifedipine. These results are the first demonstration thatin vitro, asin vivo, depolarization increases TH expression in olfactory bulb and that L-type calcium channels mediate this activity-dependent regulation of the dopamine phenotype.
A Role for Cyclin-Dependent Kinase(s) in the Modulation of Fast Anterograde Axonal Transport: Effects Defined by Olomoucine and the APC Tumor Suppressor Protein
Authors: Ratner Nancy , Bloom George S. , Brady Scott T.
Published: April 2018

Proteins that interact with both cytoskeletal and membrane components are candidates to modulate membrane trafficking. The tumor suppressor proteins neurofibromin (NF1) and adenomatous polyposis coli (APC) both bind to microtubules and interact with membrane-associated proteins. The effects of recombinant NF1 and APC fragments on vesicle motility were evaluated by measuring fast axonal transport along microtubules in axoplasm from squid giant axons. APC4 (amino acids 1034–2844) reduced only anterograde movements, whereas APC2 (aa 1034–2130) or APC3 (aa 2130–2844) reduced both anterograde and retrograde transport. NF1 had no effect on organelle movement in either direction. Because APC contains multiple cyclin-dependent kinase (CDK) consensus phosphorylation motifs, the kinase inhibitor olomoucine was examined. At concentrations in which olomoucine is specific for cyclin-dependent kinases (5 μm), it reduced only anterograde transport, whereas anterograde and retrograde movement were both affected at concentrations at which other kinases are inhibited as well (50 μm). Both anterograde and retrograde transport also were inhibited by histone H1 and KSPXK peptides, substrates for proline-directed kinases, including CDKs. Our data suggest that CDK-like axonal kinases modulate fast anterograde transport and that other axonal kinases may be involved in modulating retrograde transport. The specific effect of APC4 on anterograde transport suggests a model in which the binding of APC to microtubules may limit the activity of axonal CDK kinase or kinases in restricted domains, thereby affecting organelle transport.
Decreased Presynaptic Sensitivity to Adenosine after Cocaine Withdrawal
Authors: Manzoni Olivier , Pujalte Didier , Williams John , Bockaert Joël
Published: April 2018

The nucleus accumbens (NAc) is a site mediating the rewarding properties of drugs of abuse, such as cocaine, amphetamine, opiates, nicotine, and alcohol (Wise and Bozarth, 1987; Koob, 1992; Samson and Harris, 1992; Woolverton and Johnson, 1992; Self and Nestler, 1995;Pontieri et al., 1996). Acute cocaine has been shown to decrease excitatory synaptic transmission mediated by the cortical afferents to the NAc (Nicola et al., 1996), but the effects of long-term cocaine treatment and withdrawal have not been explored. Here, we report that long-term (1 week) withdrawal from chronic cocaine reduced the potency of adenosine to presynaptically inhibit glutamate (Glu) release by activating adenosine A1 receptors. Adenosine A1 receptors were not desensitized, because the potency of the metabolically stable adenosine analog N6-cyclopentyl-adenosine was unchanged after chronic cocaine withdrawal. When adenosine transporters were blocked, the potency of adenosine to inhibit Glu release from naive and cocaine-withdrawn NAc slices was similar. These results suggest that one of the long-term consequences of cocaine withdrawal is an augmented uptake of adenosine. This long-lasting change expressed at the presynaptic excitatory inputs to the medium spiny output neurons in the NAc may help identify new therapeutic targets for the treatment of drug abuse.
Long-Term Dietary Strawberry, Spinach, or Vitamin E Supplementation Retards the Onset of Age-Related Neuronal Signal-Transduction and Cognitive Behavioral Deficits
Authors: Joseph J. A. , Shukitt-Hale B. , Denisova N. A. , Prior R. L. , Cao G. , Martin A. , Taglialatela G. , Bickford P. C.
Published: April 2018

Recent research has indicated that increased vulnerability to oxidative stress may be the major factor involved in CNS functional declines in aging and age-related neurodegenerative diseases, and that antioxidants, e.g., vitamin E, may ameliorate or prevent these declines. Present studies examined whether long-term feeding of Fischer 344 rats, beginning when the rats were 6 months of age and continuing for 8 months, with diets supplemented with a fruit or vegetable extract identified as being high in antioxidant activity, could prevent the age-related induction of receptor-mediated signal transduction deficits that might have a behavioral component. Thus, the following parameters were examined: (1) oxotremorine-enhanced striatal dopamine release (OX-K+-ERDA), (2) cerebellar β receptor augmentation of GABA responding, (3) striatal synaptosomal45Ca2+clearance, (4) carbachol-stimulated GTPase activity, and (5) Morris water maze performance. The rats were given control diets or those supplemented with strawberry extracts (SE), 9.5 gm/kg dried aqueous extract (DAE), spinach (SPN 6.4 gm/kg DAE), or vitamin E (500 IU/kg). Results indicated that SPN-fed rats demonstrated the greatest retardation of age-effects on all parameters except GTPase activity, on which SE had the greatest effect, whereas SE and vitamin E showed significant but equal protection against these age-induced deficits on the other parameters. For example, OX-K+-ERDA enhancement was four times greater in the SPN group than in controls. Thus, phytochemicals present in antioxidant-rich foods such as spinach may be beneficial in retarding functional age-related CNS and cognitive behavioral deficits and, perhaps, may have some benefit in neurodegenerative disease.