bluuebunny/crossref_metadata_2025 huggingface dataset:
Modulation of Voltage-Gated Calcium Channels by Orphanin FQ in Freshly Dissociated Hippocampal Neurons
Authors: Knoflach Frederic , Reinscheid Rainer K. , Civelli Olivier , Kemp John A.
Published: April 2018

Orphanin FQ (OFQ) has recently been reported to be an endogenous ligand for the opioid-like LC132 receptor. The effect of OFQ on high voltage-gated calcium channels (VGCCs) was examined in freshly dissociated rat pyramidal neurons using the whole-cell configuration of the patch-clamp technique. High-threshold Ba2+currents were reversibly inhibited by OFQ. The depression of the currents was associated with a slowed rate of activation and a change in the activationI–Vrelationship at step potentials higher than +30 mV. In concentration–response experiments, a mean (±SEM) pEC50value of 7.0 ± 0.07 and a Hill coefficient of 1.5 ± 0.08 (n = 5) were obtained. The near-maximum inhibition of the Ba2+currents by OFQ (1 μm) amounted to 31 ± 2.2% of control (n = 15). Opioid receptors could not account for the effects of OFQ on VGCCs, because naloxone, a broad spectrum μ-, δ-, and κ-receptor antagonist, did not reduce the effectiveness of OFQ. When GTP-γ-S was included in the pipette, the depression of the currents by OFQ was irreversible, whereas currents from neurons preincubated with pertussis toxin were not inhibited by OFQ, consistent with the involvement of a PTX-sensitive G-protein. When selective blockers of VGCCs were used, it was demonstrated that all subtypes of VGCCs were affected by OFQ. In conclusion, the effect of OFQ on VGCCs expressed in hippocampal CA3 and CA1 neurons may play an important role in the regulation of hippocampal cell excitability and neurotransmitter release.
Ryanodine-Sensitive Component of Calcium Transients Evoked by Nerve Firing at Presynaptic Nerve Terminals
Authors: Peng Yan-yi
Published: April 2018

Whether Ca2+released from stores within the presynaptic nerve terminals also contributes to the Ca2+elevation evoked by action potentials was tested in intact bullfrog sympathetic ganglia. Intraterminal Ca2+transients (Δ[Ca2+]i) were evoked by electrical shocks to the presynaptic nerves at 20 Hz and were monitored by fura-2 fluorimetry. Ca2+released through intraterminal ryanodine-sensitive channels accounted for 46% of the peak Ca2+elevation. Moreover, in half of the terminals when intraterminal release was blocked by ryanodine, Δ[Ca2+]ireached a plateau at 200 ± 24 nm. Because 20 Hz is a frequency favorable for the release of a neuropeptide, luteinizing hormone releasing hormone (LHRH) from these presynaptic nerve terminals, and because the threshold level for LHRH release is 186 nm, intraterminal Ca2+release during nerve firing is likely to play a major role in regulating LHRH release. The intraterminal ryanodine channels were facilitated by caffeine as in other tissue. The releasable ryanodine-sensitive store could elevate the intraterminal [Ca2+] by an amount as high as 1.6 μmat a rate as fast as 250 nm/sec. The store could be refilled within 100 sec after a maximal discharge of its content by 20 Hz firing. Oscillation of [Ca2+]ievoked by 20 Hz nerve firing occurred in normal Ringer solution, in ryanodine, and in caffeine with a periodicity of ∼10 sec. Besides the facilitatory effects on the ryanodine-sensitive channels, caffeine also had inhibitory effects on Δ[Ca2+]ivia its action on a different process.
Anion Conductance Behavior of the Glutamate Uptake Carrier in Salamander Retinal Glial Cells
Authors: Billups Brian , Rossi David , Attwell David
Published: April 2018

Glutamate uptake is driven by the cotransport of Na+ions, the countertransport of K+ions, and either the countertransport of OH−or the cotransport of H+ions. In addition, activating glutamate uptake carriers has been shown to lead to activation of an anion conductance present in the carrier structure. Here we characterize the ion selectivity and gating of this anion conductance. The conductance is small with Cl−as the permeant anion, but it is large with NO3−or ClO4−present, undermining the earlier use of NO3−and ClO4−to suggest that OH−countertransport rather than H+cotransport helps drive uptake. Activation of the anion conductance can be evoked by extra- or intracellular glutamate and can occur even when glutamate transport is inhibited. By running the carrier backward and detecting glutamate release with AMPA receptors in neurons placed near the glial cells, we show that anion flux is not coupled thermodynamically to glutamate movement, but OH−/H+transport is. The possibility that cell excitability is modulated by the anion conductance associated with glutamate uptake suggests a target for therapeutic drugs to reduce glutamate release in conditions like epilepsy.
Hippocampal Cell Responses in Mice with a Targeted Glucocorticoid Receptor Gene Disruption
Authors: Hesen Wouter , Karst Henk , Meijer Onno , Cole Tim J. , Schmid Wolfgang , de Kloet E. Ronald , Schütz Gunther , Joëls Marian
Published: April 2018

Previous studies in rats have shown that cellular properties of hippocampal CA1 neurons are under coordinative control of mineralocorticoid and glucocorticoid receptors (MRs and GRs, respectively). In the present study, we examined electrical properties under conditions of exclusive MR occupation, by using mice with a genetic defect in GRs obtained by homologous recombination techniques. It appeared that in the animals homozygous for the genetic defect, the properties studied, i.e., the voltage-gated Ca currents and responses to serotonin and the cholinergic analog carbachol, resembled the effects observed in adrenalectomized mice, i.e., when no steroid receptors are activated. This may point to the necessity of functional GRs for the development of MR-induced actions. Ca current amplitude and transmitter responses in the heterozygous animals, which combine a reduced amount of GRs in the hippocampus with relatively high circulating levels of corticosterone, were large compared with those in the wild-type controls; this resembles the responses that were observed previously in rats subjected to a very high dose of corticosterone. These findings exemplify the use of GR knockout mice for the study of cellular properties in the brain. Further substantiation of the observations, however, awaits the development of site-specific, inducible GR knockouts.
Amino Acid Signatures in the Primate Retina
Authors: Kalloniatis Michael , Marc Robert E. , Murry Ralph F.
Published: April 2018

Pattern recognition of amino acid signals partitions virtually all of the macaque retina into 16 separable biochemical theme classes, some further divisible by additional criteria. The photoreceptor→bipolar cell→ganglion cell pathway is composed of six separable theme classes, each possessing a characteristic glutamate signature. Neuronal aspartate and glutamine levels are always positively correlated with glutamate signals, implying that they largely represent glutamate precursor pools. Amacrine cells may be parsed into four glycine-dominated (including one glycine/GABA immunoreactive population) and four GABA-dominated populations. Horizontal cells in central retina possess a distinctive GABA signature, although their GABA content is constitutively lower than that of amacrine cells and shows both regional and sample variability. Finally, a taurine–glutamine signature defines Müller’s cells. We thus have established the fundamental biochemical signatures of the primate retina along with multiple metabolic subtypes for each neurochemical class and demonstrated that virtually all neuronal space can be accounted for by cells bearing characteristic glutamate, GABA, or glycine signatures.
Constructing a New Nigrostriatal Pathway in the Parkinsonian Model with Bridged Neural Transplantation in Substantia Nigra
Authors: Zhou Feng C. , Chiang Yung H. , Wang Yun
Published: April 2018

The physical repair and restoration of a completely damaged pathway in the brain has not been achieved previously. In a previous study, using excitatory amino acid bridging and fetal neural transplantation, we demonstrated that a bridged mesencephalic transplant in the substantia nigra generated an artificial nerve pathway that reinnervated the striatum of 6-hydroxydopamine (6-OHDA)-lesioned rats. In the current study, we report that a bridged mesencephalic transplant can anatomically, neurochemically, and functionally reinstate the 6-OHDA-eradicated nigro-striatal pathway. An excitatory amino acid, kainic acid, laid down in a track during the transplant generated a trophic environment that effectively guided the robust growth of transplanted neuronal fibers in a bundle to innervate the distal striatum. Growth occurred at the remarkable speed of ∼200 μm/d. Two separate and distinct types of dopamine (DA) innervation from the transplant have been achieved for the first time: (1) DA innervation of the striatum, and (2) DA innervation of the pars reticularis of the substantia nigra. In addition, neuronal tracing revealed that reciprocal connections were achieved. The grafted DA neurons in the SNr innervated the host’s striatum, whereas the host’s striatal neurons, in turn, innervated the graft within 3–8 weeks. Electrochemical volt- ammetry recording revealed the restoration of DA release and clearance in a broad striatal area associated with the DA reinnervation. Furthermore, the amphetamine-induced rotation was attenuated, which indicates that the artificial pathways were motor functional. This study provides additional evidences that our bridged transplantation technique is a potential means for the repair of a completely damaged neuronal pathway.
Ovarian Steroid Regulation of Tryptophan Hydroxylase mRNA Expression in Rhesus Macaques
Authors: Pecins-Thompson Melanie , Brown Nancy A. , Kohama Steven G. , Bethea Cynthia L.
Published: April 2018

Progesterone (P) stimulates prolactin secretion through an unknown neural mechanism in estrogen (E)-primed female monkeys. Serotonin is a stimulatory neurotransmitter in prolactin regulation, and this laboratory has shown previously that E induces progestin receptors (PR) in serotonin neurons. Therefore, we questioned whether E and/or E+P increased serotonin neural function. The expression of mRNA for tryptophan hydroxylase (TPH) was examined in ovariectomized (spayed) control, E-treated (28 d), and E+P-treated monkeys (14 d E and 14 d E+P) usingin situhybridization and a 249 bp TPH cRNA probe generated with RT-PCR (n = 5 animals/group). Densitometric analysis of film autoradiographs revealed a ninefold increase in TPH mRNA in E-treated macaques compared to spayed animals (p < 0.05). With supplemental P treatment, TPH mRNA signal was increased fivefold over spayed animals (p < 0.05), but was not significantly different compared to E-treated animals. These results were verified by grain counts from photographic emulsion-coated slides. There were significantly higher single-cell levels of TPH mRNA in serotonergic neurons of the dorsal raphe in E- and E+P-treated groups (p < 0.05). These data indicate that E induces TPH gene expression in nonhuman primates and that the addition of P has little additive effect on TPH gene expression. Thus, the action of P on prolactin secretion is probably not mediated at the level of TPH gene transcription. However, because P increases raphe serotonin content in E-primed rodents, the possibility remains that P may have other actions on post-translational processing or enzyme activity.
Tolerance to Sound Intensity of Binaural Coincidence Detection in the Nucleus Laminaris of the Owl
Authors: Peña Jose Luis , Viete Svenja , Albeck Yehuda , Konishi Masakazu
Published: April 2018

Neurons of the owl’s nucleus laminaris serve as coincidence detectors for measurement of interaural time difference. The discharge rate of nucleus laminaris neurons for both monaural and binaural stimulation increased with sound intensity until they reached an asymptote. Intense sounds affected neither the ratio between binaural and monaural responses nor the interaural time difference for which nucleus laminaris neurons were selective. Theoretical analysis showed that high afferent discharge rates cause coincidence detectors with only excitatory input to lose their selectivity for interaural time difference when coincidence of impulses from the same side becomes as likely as that of impulses from the two sides. We hypothesize that inhibitory input whose strength increases with sound intensity protects nucleus laminaris neurons from losing their sensitivity to interaural time difference with intense sounds.
Heteromultimerization of G-Protein-Gated Inwardly Rectifying K+Channel Proteins GIRK1 and GIRK2 and Their Altered Expression inweaverBrain
Authors: Liao Y. Joyce , Jan Yuh Nung , Jan Lily Yeh
Published: April 2018

Theweaver(wv) gene (GIRK2) is a member of the G-protein-gated inwardly rectifying potassium (GIRK) channel family, known effectors in the signal transduction pathway of neurotransmitters such as acetylcholine, dopamine, opioid peptides, and substance P in modulation of neurotransmitter release and neuronal excitability. GIRK2 immunoreactivity is found in but not limited to brain regions known to be affected inwvmice, such as the cerebellar granule cells and dopaminergic neurons in the substantia nigra pars compacta. It is also observed in the ventral tegmental area, hippocampus, cerebral cortex, and thalamus. GIRK2 and GIRK1, a related family member, have overlapping yet distinct distributions in rat and mouse brains. In regions where both channel proteins are expressed, such as the cerebral cortex, hippocampus, and cerebellum, they can be co-immunoprecipitated, indicating that they interact to form heteromeric channelsin vivo. In the brain of thewvmouse, GIRK2 expression is decreased dramatically. In regions where GIRK1 and GIRK2 distributions overlap, both GIRK1 and GIRK2 expressions are severely disrupted, probably because of their co-assembly. The expression patterns of these GIRK channel subunits provide a basis for consideration of the machinery for neuronal signaling as well as the differential effects of thewvmutation in various neurons.
Coordinate System for Learning in the Smooth Pursuit Eye Movements of Monkeys
Authors: Kahlon Maninder , Lisberger Stephen G.
Published: April 2018

Learning was induced in smooth pursuit eye movements by repeated presentation of targets that moved at one speed for 100 msec and then changed to a second, higher or lower, speed. The learned changes, measured as eye acceleration for the first 100 msec of pursuit, were largest in a “late” interval from 50 to 80 msec after the onset of pursuit and were smaller and less consistent in the earliest 30 msec of pursuit. In each experiment, target motion in one direction consisted of learning trials, whereas target motion in the opposite (control) direction consisted of trials in which targets moved at a constant speed for the entire duration of the trial. Under these conditions, the learning did not generalize to the control direction. For target motion in the learning direction, the changes in pursuit generalized to responses evoked by targets moving at speeds ranging from 15 to 45°/sec as well as to targets of different colors and sizes. Although learning was induced at the initiation of pursuit, it generalized to the response to image motion in the learning direction when it was presented during pursuit in the learning direction. However, learning did not generalize to the response to image motion in the learning direction when it was presented during pursuit in the control direction. The results suggest that the learning does not occur in purely sensory or motor coordinates but in an intermediate reference frame at least partly defined by the direction of eye movement. The selectivity of learning provides new evidence for a previously hypothesized neural “switch” that gates visual information on the basis of movement direction. This selectivity also suggests that the locus of pursuit learning is in pathways related to the operation of the switch.
An Explanation for Reflex Blink Hyperexcitability in Parkinson’s Disease. I. Superior Colliculus
Authors: Basso Michele A. , Powers Alice S. , Evinger Craig
Published: April 2018

Hyperexcitable reflex blinks are a cardinal sign of Parkinson’s disease. We investigated the neural circuit through which a loss of dopamine in the substantia nigra pars compacta (SNc) leads to increased reflex blink excitability. Through its inhibitory inputs to the thalamus, the basal ganglia could modulate the brainstem reflex blink circuits via descending cortical projections. Alternatively, with its inhibitory input to the superior colliculus, the basal ganglia could regulate brainstem reflex blink circuits via tecto-reticular projections. Our study demonstrated that the basal ganglia utilizes its GABAergic input to the superior colliculus to modulate reflex blinks. In rats with previous unilateral 6-hydroxydopamine (6-OHDA) lesions of the dopamine neurons of the SNc, we found that microinjections of bicuculline, a GABA antagonist, into the superior colliculus of both alert and anesthetized ratseliminatedthe reflex blink hyperexcitability associated with dopamine depletion. In normal, alert rats, decreasing the basal ganglia output to the superior colliculus by injecting muscimol, a GABA agonist, into the substantia nigra pars reticulata (SNr) markedlyreducedblink amplitude. Finally, brief trains of microstimulation to the superior colliculusreducedblink amplitude. Histological analysis revealed that effective muscimol microinjection and microstimulation sites in the superior colliculus overlapped the nigro-tectal projection from the basal ganglia. These data support models of Parkinsonian symtomatology that rely on changes in the inhibitory drive from basal ganglia output structures. Moreover, they support a model of Parkinsonian reflex blink hyperexcitability in which the SNr–SC target projection is critical.
The Sympathetic Nervous System Contributes to Capsaicin-Evoked Mechanical Allodynia But Not Pinprick Hyperalgesia in Humans
Authors: Liu Maywin , Max Mitchell B. , Parada Suzan , Rowan Janet S. , Bennett Gary J.
Published: April 2018

The contribution of the sympathetic nervous system (SNS) to pain, mechanical allodynia (MA), and hyperalgesia in humans is controversial. A clearer understanding is crucial to guide therapeutic use of sympatholytic surgery, blocks, and drug treatments. In rats, capsaicin-evoked MA, and to some extent, pinprick hyperalgesia (PPH), can be blocked with α-adrenoreceptor antagonists. In this study, we examined the contribution of the SNS to MA and PPH in normal human subjects by blocking α-adrenoreceptors with intravenous phentolamine.

In a double-blinded, placebo-controlled, crossover study, subjects were given IV saline or phentolamine, 1 mg/kg over 20 min. Ten minutes after the start of the infusion, subjects received 100 μg of intradermal capsaicin on the foot dorsum with the temperature of the injected site clamped at 36°C. The temperature of the uninjected foot was used to monitor the degree of α-adrenoreceptor blockade produced by phentolamine. Ongoing pain and MA and PPH areas were measured every 5 min for 60 min.

A significantly greater increase in temperature on the uninjected foot was seen during the phentolamine infusion compared with the saline infusion, indicating α-adrenergic blockade. Significantly less MA was observed with the phentolamine infusion 10–25 min after capsaicin injection than with the saline infusion. No significant differences in ongoing pain or PPH areas were seen between the two infusions at any time.

Our results suggest that capsaicin-evoked MA and PPH have different mechanisms, with the SNS having a role in MA but not in PPH or ongoing pain.
Metabolic and Genetic Analyses of Apoptosis in Potassium/Serum-Deprived Rat Cerebellar Granule Cells
Authors: Miller Timothy M. , Johnson Jr. Eugene M.
Published: April 2018

Cerebellar granule cells maintained in medium containing serum and 25 mmpotassium undergo an apoptotic death within 96 hr when switched to serum-free medium with 5 mmpotassium. Because large numbers of apparently homogeneous neurons can be obtained, this represents a potentially useful model of neuronal programmed cell death (PCD). Analysis of the time course and extent of death after removal of either serum or K+alone demonstrated that a fast-dying (T1/2= 4 hr) population (20%) responded to serum deprivation, whereas a slow-dying (T1/2= 25 hr) population (80%) died in response to K+deprivation. Taking advantage of the complete death after removing both K+and serum, changes in metabolic events and mRNA levels were analyzed in this model. Glucose uptake, protein synthesis, and RNA synthesis fell to <35% of control by 9 hr after potassium/serum deprivation, a time when 85% of the cells were still viable. The pattern of the fall in these metabolic parameters was similar to that reported for trophic factor-deprived sympathetic neurons. Most mRNAs decreased markedly after K+/serum deprivation. Levels ofc-junmRNA increased fivefold in potassium/serum-deprived granule cells;c-junis required for cell death of sympathetic neurons. mRNA levels ofcyclin D1,c-myb,collagenase, andtransinremained relatively constant in potassium/serum-deprived granule cells. These data demonstrate the existence of two populations of granule cells with respect to cell death and define common metabolic and genetic events involved in neuronal PCD.
Ionic Currents Underlying Developmental Regulation of Repetitive Firing inAplysiaBag Cell Neurons
Authors: Nick Teresa A. , Kaczmarek Leonard K. , Carew Thomas J.
Published: April 2018

We have investigated the developmental regulation of the ability to fire repetitively in the bag cell neurons ofAplysia californica, a neuronal system in which the behavioral effects of repetitive firing are well characterized. Adult bag cell neurons exhibit an afterdischarge, consisting of prolonged depolarization and repetitive firing, which causes the release of several peptides from these neurons that induce egg-laying behaviors. Afterdischarge can be triggeredin vitroby a variety of stimuli, including electrical stimulation and exposure to the potassium channel blocker tetraethyl ammonium chloride (TEA). In contrast to adults, juvenile neurons did not exhibit afterdischarge in response to pleural–abdominal connective shock or TEA. Juvenile neurons did exhibit, however, prolonged depolarizations in the presence of TEA, perhaps reflecting the anlage of the mechanism responsible for afterdischarge in the adult.

To investigate developmental mechanisms underlying the regulation of repetitive firing, we compared ionic currents in adult and juvenile bag cell neurons. We found that during the period in which these neurons acquire the capacity to fire repetitively, a number of currents are regulated: (1) three K+currents decrease (Ca2+-dependent K+and two components of voltage-dependent delayed-rectifier K+current); (2) A-type K+current increases; and (3) two Ca2+currents increase (basal and PKC-activated). This pattern is consistent with the increase in the ability to fire repetitively that we observe during maturation: our results indicate that developmental control of repetitive firing in this system is accompanied by selective regulation of specific ionic currents which, after maturation, play important roles in generating the afterdischarge and triggering egg-laying behaviors.
cAMP Levels Increased by Activation of Metabotropic Glutamate Receptors Correlate with Visual Plasticity
Authors: Reid Silvia N. M. , Daw Nigel W. , Gregory Douglas S. , Flavin Helen
Published: April 2018

We have investigated the cAMP level increased by stimulation of metabotropic glutamate receptors (mGluRs) in cat visual cortex during development. The cAMP level increases activated by the general mGluR agonist (1S,3R)-1-amino-1,3-cyclopentane-dicarboxylic acid (ACPD) were closely correlated with the critical period for ocular dominance plasticity in both light- and dark-reared animals. Activation of either group I or group II mGluRs increased the cAMP level. Group II mGluR activation also reduced the forskolin-stimulated cAMP increase. The correlation was emulated by a mixture of groups I, II, and III mGluR agonists but not by agonists applied singly; therefore, the correlation is attributable to activation of multiple groups of mGluRs. The cAMP level increased by the mixture was greater than the sum of the increases produced by the agonists applied singly (super-additive effect), suggesting an interaction between the G-proteins and/or second messengers controlled by these mGluRs. The basal cAMP level also correlated closely with the critical period until shortly after the peak of the critical period. Therefore, the major factor that contributes to the correlation between the ACPD-stimulated cAMP increase and the peak of the critical period is the basal level of cAMP: the activation of multiple mGluRs amplifies the basal cAMP. We suggest that both basal activity of cAMP production and activation of mGluRs may be important in plasticity in the visual cortex.
Restriction in Cell Fates of Developing Spinal Cord Cells Transplanted to Neural Crest Pathways
Authors: Korade Z̆eljka , Frank Eric
Published: April 2018

At early neural tube stages, individual stem cells can generate neural crest cells as well as dorsal or ventral spinal cord cells. To determine whether this pluripotency is lost as development proceeds, we back-transplanted quail spinal cells from different developmental stages and different spinal locations into the crest migratory pathways of st 16–20 chicken host embryos. The transplanted spinal cells from st 27 dorsal cord and st 18 ventral cord differentiated within the new crest environment into sensory and sympathetic neurons, satellite and Schwann cells, and melanocytes. St 27 ventral cells still generated several crest derivatives but not sensory or sympathetic neurons. This loss in ability to produce neurons correlates with the end of neurogenesis in ventral cord. The end of neurogenesis in the cord, therefore, results from an intrinsic change in the potential of spinal neuroepithelial cells to generate neurons.
Release of Vasopressin within the Rat Paraventricular Nucleus in Response to Emotional Stress: A Novel Mechanism of Regulating Adrenocorticotropic Hormone Secretion?
Authors: Wotjak Carsten T. , Kubota Masaharu , Liebsch Gudrun , Montkowski Alexandra , Holsboer Florian , Neumann Inga , Landgraf Rainer
Published: April 2018

The effects of emotional stressors on the release of arginine vasopressin (AVP) and oxytocin (OXT) within the rat hypothalamus and the origin and physiological significance of AVP released within the hypothalamic paraventricular nucleus (PVN) were investigated. First, adult male Wistar rats with a microdialysis probe aimed at the PVN or the supraoptic nucleus were exposed to either a dominant male rat (social defeat) or a novel cage. Release of AVP within the PVN was significantly increased in response to social defeat but not to novelty. In contrast to an activation of the hypothalamic–pituitary–adrenal (HPA) system, neither stressor stimulated the hypothalamic–neurohypophysial system (unchanged plasma AVP and OXT and unchanged release within the supraoptic nucleus [AVP] and the PVN [OXT]). Next, we demonstrated by simultaneous microdialysis of the suprachiasmatic nucleus and the PVN that AVP measured in PVN dialysates during social defeat was probably of intranuclear origin. Finally, a mixture of a V1 AVP and the α-helical corticotropin-releasing hormone (CRH) receptor antagonists administered via inverse microdialysis into the PVN caused a significant increase in the plasma adrenocorticotropic hormone (ACTH) concentration compared with vehicle-treated controls both under basal conditions and during social defeat, indicating inhibitory effects of intra-PVN-released AVP and/or CRH on HPA system activity. The antagonists failed to affect anxiety-related behavior of the animals as assessed with the elevated plus-maze. Taken together, our results show for the first time that AVP is released within the PVN in response to an emotional stressor. We hypothesize that this intranuclear release provides a negative tonus on ACTH secretion.
Dopamine and Spatial Working Memory in Rats and Monkeys: Pharmacological Reversal of Stress-Induced Impairment
Authors: Murphy Beth L. , Arnsten Amy F. T. , Jentsch J. David , Roth Robert H.
Published: April 2018

The anxiogenic benzodiazepine inverse agonist FG7142 increases dopamine turnover in rodent prefrontal cortex but not in other dopamine terminal field areas. FG7142-induced increases in prefrontal cortical dopamine receptor stimulation impair prefrontal-dependent, but not nonprefrontal-dependent, cognitive tasks in rats and monkeys. The degree of impairment correlates with levels of prefrontal cortical dopamine turnover in rats and can be blocked in rats and monkeys with dopamine receptor antagonists, suggesting that increased dopamine turnover is directly related to the cognitive deficits.

The current study examined nondopaminergic drug effects on FG7142-perturbed biochemistry and cognition. Both the noradrenergic α-2 agonist clonidine and the glycine/NMDA antagonist (+)HA966 prevented the FG7142-induced increase in dopamine turnover in rodent prefrontal cortex. Infusion of (+)HA966 into the ventral tegmental area (VTA) also blocked this increase in dopamine turnover, indicating that critical modulatory effects of (+)HA966 on FG7142-induced changes in dopamine turnover are occurring at the level of mesoprefrontal dopamine neuron cell bodies. Systemic (+)HA966 and clonidine, but not propranolol ord-cycloserine, prevented FG7142-associated spatial working memory deficits in rats and monkeys. These results support the idea of a critical range of dopamine turnover for optimal prefrontal cortical cognitive functioning, with excessive dopamine turnover leading to cognitive impairment. These studies also provide evidence for the regulation of prefrontal cortical dopamine turnover and cognition by multiple neurotransmitter systems and suggest that the VTA is an important regulatory site for these effects.
Dynamic Changes in Striatal Dopamine D2and D3Receptor Protein and mRNA in Response to 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine (MPTP) Denervation in Baboons
Authors: Todd Richard D. , Carl Juanita , Harmon Steven , O’Malley Karen L. , Perlmutter Joel S.
Published: April 2018

Loss of nigrostriatal neurons leads to striatal dopamine deficiency and subsequent development of parkinsonism. The effects of this denervation on D2-like receptors in striatum remain unclear. Most studies have demonstrated increases in striatal dopamine D2-like receptors in response to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-mediated denervation, but others have found either decreases or no change in binding. To clarify the response to denervation, we have investigated the time-dependent changes in dopamine D2, D3, and D4receptor protein and mRNA levels in unilaterally MPTP-lesioned baboons. MPTP (0.4 mg/kg) was infused into one internal carotid artery, producing a contralateral hemi-parkinsonian syndrome. After MPTP treatment, the animals were maintained for 17–480 d and then euthanized. MPTP decreased ipsilateral dopamine content by >90%, which did not change with time. Ipsilateral D2-like receptor binding in caudate and putamen initially decreased then increased two- to sevenfold over the first 100 d and returned to near baseline levels by 480 d. Relative levels of D2mRNA were essentially unchanged over this period. D4mRNA was not detected. In contrast, D3mRNA increased sixfold by 2 weeks and then decreased. At the peak period of increase in binding sites, all D2-like receptors were in a micromolar affinity agonist-binding state, implying an increase in uncoupled D2but not D3receptor protein. Taken together, these data suggest that MPTP-induced changes in D2-like dopamine receptors are complex and include translational or post-translational mechanisms.
Early and Later Adoptions Have Different Long-Term Effects on Male Rat Offspring
Authors: Barbazanges Arnaud , Vallée Monique , Mayo Willy , Day Jamie , Simon Hervé , Le Moal Michel , Maccari Stefania
Published: April 2018

Both prenatal and postnatal environmental factors exert complex influences on the development of an organism. Previous studies have demonstrated that intervening events during the prenatal period can have different and even opposite effects than similar intervening events occurring in the postnatal period. We have reported previously that early postnatal adoption prevents prenatal stress-induced long-term impairments in glucocorticoid feedback. To characterize further the effects of adoptions during the postnatal period, adoptions have been performed at different times, and the effect on the postnatal ontogeny of the hypothalamo–pituitary–adrenal axis has been investigated. Adoptions were performed during the first hour after birth (A1) and on the fifth (A5) and twelfth (A12) days after birth. At each of these times, other litters (S1, S5, S12) underwent a “separation” controlling for the 1 min maternal separation necessary for the adoptions. Locomotor behavior, cognition, and stress-induced corticosterone secretion in the adult male offspring have been examined, along with maternal behavior. Early adoption (A1) was found to prevent the prolonged stress-induced secretion of corticosterone evident in early separated (S1) offspring. Similarly, A1 rats demonstrated lower novelty-induced locomotion and improved recognition performance in a Y-maze compared to S1 offspring. However, later adoption (A5, A12) prolonged stress-induced corticosterone secretion, increased the locomotor response to novelty, and disrupted cognitive performance in the offspring. Only the early adoption increased maternal licking behavior, a factor that may have a protective effect on the pups. Taken together, these results suggest that the same postnatal manipulation realized at different times can induce different, or even opposite, effects on the behavioral and neuroendocrine characteristics of the adult offspring.
Visual Pigment Assignments in Regenerated Retina
Authors: Cameron David A. , Cornwall M. Carter , MacNichol Jr. Edward F.
Published: April 2018

Retinas of adult teleost fish can regenerate after injury. Two important issues regarding this phenomenon are the assembly of the regenerated retina and the neuronal images of the visual scene that the regenerated retina produces. Here we report experiments in which the visual pigment content of photoreceptors derived from native and regenerated sunfish retinas was determined by microspectrophotometry. In native retina, there is an apparently perfect correspondence between cone morphology and visual pigment content; all rods contain a middle-wavelength pigment, all single cones contain a different middle-wavelength pigment, and all double cone members contain a long-wavelength pigment. The visual pigments in regenerated rods and double cones were the same as in native retina; however, triple cones, a morphology never observed in native retina, contained the long-wavelength pigment. Moreover, although ∼60% of regenerated single cones contained the expected middle-wavelength pigment, all other single cones contained the long-wavelength pigment. This mismatch between morphology of regenerated single cones and their visual pigment assignment indicated the following: (1) There is a degree of independence between the mechanisms that establish cone morphology and pigment content during regeneration, which suggests that cone photoreceptor regeneration is not a straightforward recapitulation of the normal cone photoreceptor developmental plan. (2) Although anomalous, the long-wavelength single cones may enable regenerated retina to restore the native spectral sampling of the visual scene.
Overexpression of Ca2+/Calmodulin-Dependent Protein Kinase II in PC12 Cells Alters Cell Growth, Morphology, and Nerve Growth Factor-Induced Differentiation
Authors: Massé Thierry , Kelly Paul T.
Published: April 2018

To examine the role of Ca2+/calmodulin-dependent protein kinase II (CaMKII) in cell differentiation and neuronal functions, stable transformants of PC12 cells were established that expressed levels of the α-subunit of CaMKII (αCaMKII) equivalent to mammalian neurons. The expression of the transfected αCaMKII gene or the endogenous βCaMKII gene was monitored by RNase protection assays, and αCaMKII protein expression was determined by Western blots. Several PC12-derived clones expressed amounts of αCaMKII mRNA and αCaMKII protein similar to that of hippocampal tissues and several orders of magnitude greater than untransfected PC12 cells. CaMKII catalytic activity was four times higher in extracts from αCaMKII-overexpressing compared with untransfected PC12 cells. All clones overexpressing αCaMKII displayed altered cellular growth and adhesion properties including increased cell-to-substrate adhesion, decreased cell-to-cell adhesion, enhanced contact inhibition, and prolonged survival at confluency. Furthermore, the αCaMKII activity in overexpressing PC12 cells inhibited neurite elongation during NGF-induced differentiation. Inhibition of CaMKII activityin vivowith KN-62 caused the morphological phenotypes of αCaMKII-overexpressing cells to partially revert to that of untransfected PC12 cells. These results show that αCaMKII catalytic activity affects growth, morphology, and NGF-induced differentiation of PC12 cells.
Amyloid β-Peptide Impairs Glucose Transport in Hippocampal and Cortical Neurons: Involvement of Membrane Lipid Peroxidation
Authors: Mark Robert J. , Pang Zhen , Geddes James W. , Uchida Koji , Mattson Mark P.
Published: April 2018

A deficit in glucose uptake and a deposition of amyloid β-peptide (Aβ) each occur in vulnerable brain regions in Alzheimer’s disease (AD). It is not known whether mechanistic links exist between Aβ deposition and impaired glucose transport. We now report that Aβ impairs glucose transport in cultured rat hippocampal and cortical neurons by a mechanism involving membrane lipid peroxidation. Aβ impaired3H-deoxy-glucose transport in a concentration-dependent manner and with a time course preceding neurodegeneration. The decrease in glucose transport was followed by a decrease in cellular ATP levels. Impairment of glucose transport, ATP depletion, and cell death were each prevented in cultures pretreated with antioxidants. Exposure to FeSO4, an established inducer of lipid peroxidation, also impaired glucose transport. Immunoprecipitation and Western blot analyses showed that exposure of cultures to Aβ induced conjugation of 4-hydroxynonenal (HNE), an aldehydic product of lipid peroxidation, to the neuronal glucose transport protein GLUT3. HNE induced a concentration-dependent impairment of glucose transport and subsequent ATP depletion. Impaired glucose transport was not caused by a decreased energy demand in the neurons, because ouabain, which inhibits Na+/K+-ATPase activity and thereby reduces neuronal ATP hydrolysis rate, had little or no effect on glucose transport. Collectively, the data demonstrate that lipid peroxidation mediates Aβ-induced impairment of glucose transport in neurons and suggest that this action of Aβ may contribute to decreased glucose uptake and neuronal degeneration in AD.
Novel Modulatory Effect of L-Type Calcium Channels at Newly Formed Neuromuscular Junctions
Authors: Sugiura Yoshie , Ko Chien-Ping
Published: April 2018

This study aimed to examine changes of presynaptic voltage-sensitive calcium channel (VSCC) subtypes during synapse formation and regeneration in relation to transmitter release at the neuromuscular junction (NMJ). Synaptic potentials were recorded from developing rat NMJs and from regenerating mouse and frog NMJs. As in normal adult NMJs, evoked transmitter release was reduced by an N-type VSCC blocker in the frog and by a P/Q-type VSCC blocker in the mammal at immature NMJs; however, various L-type VSCC blockers, both dihydropyridine and nondihydropyridine antagonists,increasedevoked but not spontaneous release in a dose-dependent manner at newly formed NMJs. This presynaptic potentiation disappeared as NMJs matured. A rapid intracellular Ca2+buffer, bis(O-aminophenoxy)ethane-N,N,N′,N′-tetra-acetic acid-AM, prevented the potentiation effect of nifedipine, but a slow Ca2+buffer, EGTA-AM, did not. Thus, the potentiation effect of L-type blockers requires Ca2+transients. Pretreatment with Ca2+-activated K+channel blockers, iberiotoxin or charybdotoxin, did not prevent potentiation by nifedipine at regenerating frog NMJs. Thus, Ca2+-activated K+channels were not likely involved in this potentiation. In contrast, no additional potentiation by nifedipine was seen in muscles pretreated with pertussis toxin (PTX), a G-protein blocker, which by itself enhances evoked transmitter release at regenerating frog NMJs. These results suggest the existence of multiple subtypes of VSCCs at newly formed motor nerve terminals. In addition to the normal N- or P/Q-type VSCCs that mediate transmitter release, L-type VSCCs may play a novel modulatory role in evoked transmitter release by activating a mechanism linked to PTX-sensitive G-proteins during synapse maturation.
Differential Regulation of Ciliary Neurotrophic Factor (CNTF) and CNTF Receptor α Expression in Astrocytes and Neurons of the Fascia Dentata after Entorhinal Cortex Lesion
Authors: Lee Mun-Yong , Deller Thomas , Kirsch Matthias , Frotscher Michael , Hofmann Hans-Dieter
Published: April 2018

Neurotrophic factors have been implicated in reactive processes occurring in response to CNS lesions. Ciliary neurotrophic factor (CNTF), in particular, has been shown to ameliorate axotomy-induced degeneration of CNS neurons and to be upregulated at wound sites in the brain. To investigate a potential role of CNTF in lesion-induced degeneration and reorganization, we have analyzed the expression of CNTF protein and CNTF receptor α (CNTFRα) mRNA in the rat dentate gyrus after unilateral entorhinal cortex lesions (ECLs), using immunocytochemistry and nonradioactivein situhybridization, respectively.

In sham-operated as in normal animals, CNTF protein was not detectable by immunocytochemistry. Starting at 3 d after ECL, upregulation of CNTF expression was observed in the ipsilateral outer molecular layer (OML). Expression was maximal at around day 7, and at this stage immunoreactivity could be specifically localized to astrocytes in the ipsilateral OML. By day 14 postlesion, CNTF immunoreactivity had returned to control levels. CNTFRα mRNA was restricted to neurons of the granule cell layer in controls. Three days postlesion, prominent CNTFRα expression was observed in the deafferented OML. A similar but less prominent response was noticed in the contralateral OML. After 10 d, CNTFRα expression had returned to control levels. Double labeling for CNTFRα mRNA and glial fibrillary acidic protein (GFAP) showed that upregulation of CNTFRα occurred in reactive, GFAP-immunopositive astrocytes of the OML. A substantial reduction of CNTFRα expression in the deafferented granule cells was transiently observed at 7 and 10 d postlesion. Our results suggest a paracrine or autocrine function of CNTF in the regulation of astrocytic and neuronal responses after brain injury.
Neurotransmitter- and Growth Factor-Induced cAMP Response Element Binding Protein Phosphorylation in Glial Cell Progenitors: Role of Calcium Ions, Protein Kinase C, and Mitogen-Activated Protein Kinase/Ribosomal S6 Kinase Pathway
Authors: Pende Mario , Fisher Tracey L. , Simpson Peter B. , Russell James T. , Blenis John , Gallo Vittorio
Published: April 2018

To understand how extracellular signals may produce long-term effects in neural cells, we have analyzed the mechanism by which neurotransmitters and growth factors induce phosphorylation of the transcription factor cAMP response element binding protein (CREB) in cortical oligodendrocyte progenitor (OP) cells. Activation of glutamate receptor channels by kainate, as well as stimulation of G-protein-coupled cholinergic receptors by carbachol and tyrosine kinase receptors by basic fibroblast growth factor (bFGF), rapidly leads to mitogen-activated protein kinase (MAPK) phosphorylation and ribosomal S6 kinase (RSK) activation. Kainate and carbachol activation of the MAPK pathway requires extracellular calcium influx and is accompanied by protein kinase C (PKC) induction, with no significant increase in GTP binding to Ras. Conversely, growth factor-stimulated MAPK phosphorylation is independent of extracellular calcium and is accompanied by Ras activation. Both basal and stimulated MAPK activity in OP cells are influenced by cytoplasmic calcium levels, as shown by their sensitivity to the calcium chelator bis(2-aminophenoxy)ethane-N,N,N′,N′-tetra-acetic acid. The kinetics of CREB phosphorylation in response to the various agonists corresponds to that of MAPK activation. Moreover, CREB phosphorylation and MAPK activation are similarly affected by calcium ions. The MEK inhibitor PD 098059, which selectively prevents activation of the MAPK pathway, strongly reduces induction of CREB phosphorylation by kainate, carbachol, bFGF, and the phorbol ester TPA. We propose that in OPs the MAPK/RSK pathway mediates CREB phosphorylation in response to calcium influx, PKC activation, and growth factor stimulation.
p53 Expression Induces Apoptosis in Hippocampal Pyramidal Neuron Cultures
Authors: Jordán Joaquı́n , Galindo Marı́a F. , Prehn Jochen H. M. , Weichselbaum Ralph R. , Beckett Michael , Ghadge Ghanashyam D. , Roos Raymond P. , Leiden Jeffrey M. , Miller Richard J.
Published: April 2018

The tumor suppressor gene p53 has been implicated in the induction of apoptosis in dividing cells. We now show that overexpression of p53 using an adenoviral vector in cultured rat hippocampal pyramidal neurons causes widespread neuronal death with features typical of apoptosis. p53 overexpression did not induce p21, bax, or mdm2 in neurons. X-irradiation of hippocampal neurons induced p53 immunoreactivity and cell death associated with features typical of apoptosis. Overexpression of a constitutively active nonphosphorylatable form of the retinoblastoma gene product blocked x-irradiation-induced neuronal death. However, overexpression of the cyclin-dependent kinase inhibitor p21 did not. Treatment of neurons with transforming growth factor-β1 protected them from x-irradiation. These results are consistent with a role for p53 in nerve cell death that is distinct from its actions relating to cell cycle arrest.
Neurotrophic Factors Increase Neuregulin Expression in Embryonic Ventral Spinal Cord Neurons
Authors: Loeb Jeffrey A. , Fischbach Gerald D.
Published: April 2018

Neuregulins (NRGs) are expressed in spinal cord motor neurons and accumulate at the neuromuscular junction where they may increase the synthesis of postsynaptic acetylcholine receptors and voltage-gated sodium channels. We demonstrate here that NRG expression is selectively increased in rat ventral spinal cord neurons at approximately the time that nerve–muscle synapses first form. A rapid increase in NRG mRNA and protein expression was inducedin vitroin cultured rat spinal motor neurons by brain-derived neurotrophic factor, neurotrophin-3, neurotrophin-4, or glial-cell-line-derived neurotrophic factor. Agrin expression was not affected by these factors over the same time course. Brain-derived neurotrophic factor, but not neurotrophin-3, selectively regulated immunoglobulin domain-containing splice variants of NRG, which are likely to be important for binding to the synaptic basal lamina. Regulation of NRG expression in motor neurons by muscle-derived neurotrophic factors may represent one portion of a reciprocal, regulatory loop that promotes neuromuscular synapse development.