Subset Of GABAergic Neurons Research Articles

Dysfunctional Parvalbumin Neurons in Schizophrenia and the Pathway to the Clinical Application of Kv3 Channel Modulators.

Based on the pathophysiological changes observed in schizophrenia, the gamma-aminobutyric acid (GABA) hypothesis may facilitate the development of targeted treatments for this disease. This hypothesis, mainly derived from postmortem brain results, postulates dysfunctions in a subset of GABAergic neurons, particularly parvalbumin-containing interneurons. In the cerebral cortex, the fast spike firing of parvalbumin-positive GABAergic interneurons is regulated by the Kv3.1 and Kv3.2 channels, which belong to a potassium channel subfamily. Decreased Kv3.1 levels have been observed in the prefrontal cortex of patients with schizophrenia, prompting the investigation of Kv3 channel modulators for the treatment of schizophrenia. However, biomarkers that capture the dysfunction of parvalbumin neurons are required for these modulators to be effective in the pharmacotherapy of schizophrenia. Electroencephalography and magnetoencephalography studies have demonstrated impairments in evoked gamma oscillations in patients with schizophrenia, which may reflect the dysfunction of cortical parvalbumin neurons. This review summarizes these topics and provides an overview of how the development of therapeutics that incorporate biomarkers could innovate the treatment of schizophrenia and potentially change the targets of pharmacotherapy.

Increased locomotor activity via regulation of GABAergic signalling in foxp2 mutant zebrafish\u2014implications for neurodevelopmental disorders

Recent advances in the genetics of neurodevelopmental disorders (NDDs) have identified the transcription factor FOXP2 as one of numerous risk genes, e.g. in autism spectrum disorders (ASD) and attention-deficit/hyperactivity disorder (ADHD). FOXP2 function is suggested to be involved in GABAergic signalling and numerous studies demonstrate that GABAergic function is altered in NDDs, thus disrupting the excitation/inhibition balance. Interestingly, GABAergic signalling components, including glutamate-decarboxylase 1 (Gad1) and GABA receptors, are putative transcriptional targets of FOXP2. However, the specific role of FOXP2 in the pathomechanism of NDDs remains elusive. Here we test the hypothesis that Foxp2 affects behavioural dimensions via GABAergic signalling using zebrafish as model organism. We demonstrate that foxp2 is expressed by a subset of GABAergic neurons located in brain regions involved in motor functions, including the subpallium, posterior tuberculum, thalamus and medulla oblongata. Using CRISPR/Cas9 gene-editing we generated a novel foxp2 zebrafish loss-of-function mutant that exhibits increased locomotor activity. Further, genetic and/or pharmacological disruption of Gad1 or GABA-A receptors causes increased locomotor activity, resembling the phenotype of foxp2 mutants. Application of muscimol, a GABA-A receptor agonist, rescues the hyperactive phenotype induced by the foxp2 loss-of-function. By reverse translation of the therapeutic effect on hyperactive behaviour exerted by methylphenidate, we note that application of methylphenidate evokes different responses in wildtype compared to foxp2 or gad1b loss-of-function animals. Together, our findings support the hypothesis that foxp2 regulates locomotor activity via GABAergic signalling. This provides one targetable mechanism, which may contribute to behavioural phenotypes commonly observed in NDDs.

Acoustic Trauma Changes the Parvalbumin-Positive Neurons in Rat Auditory Cortex.

Acoustic trauma is being reported to damage the auditory periphery and central system, and the compromised cortical inhibition is involved in auditory disorders, such as hyperacusis and tinnitus. Parvalbumin-containing neurons (PV neurons), a subset of GABAergic neurons, greatly shape and synchronize neural network activities. However, the change of PV neurons following acoustic trauma remains to be elucidated. The present study investigated how auditory cortical PV neurons change following unilateral 1 hour noise exposure (left ear, one octave band noise centered at 16 kHz, 116 dB SPL). Noise exposure elevated the auditory brainstem response threshold of the exposed ear when examined 7 days later. More detectable PV neurons were observed in both sides of the auditory cortex of noise-exposed rats when compared to control. The detectable PV neurons of the left auditory cortex (ipsilateral to the exposed ear) to noise exposure outnumbered those of the right auditory cortex (contralateral to the exposed ear). Quantification of Western blotted bands revealed higher expression level of PV protein in the left cortex. These findings of more active PV neurons in noise-exposed rats suggested that a compensatory mechanism might be initiated to maintain a stable state of the brain.

Lhx6-positive GABA-releasing neurons of the zona incerta promote sleep.

Multiple populations of wake-promoting neurons have been characterized in mammals, but few sleep-promoting neurons have been identified. Wake-promoting cell types include hypocretin and GABA (γ-aminobutyric-acid)-releasing neurons of the lateral hypothalamus, which promote the transition to wakefulness from non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. Here we show that a subset of GABAergic neurons in the mouse ventral zona incerta, which express the LIM homeodomain factor Lhx6 and are activated by sleep pressure, both directly inhibit wake-active hypocretin and GABAergic cells in the lateral hypothalamus and receive inputs from multiple sleep-wake-regulating neurons. Conditional deletion of Lhx6 from the developing diencephalon leads to decreases in both NREM and REM sleep. Furthermore, selective activation and inhibition of Lhx6-positive neurons in the ventral zona incerta bidirectionally regulate sleep time in adult mice, in part through hypocretin-dependent mechanisms. These studies identify a GABAergic subpopulation of neurons in the ventral zona incerta that promote sleep.

Molecular heterogeneity of aggrecan-based perineuronal nets around five subclasses of parvalbumin-expressing neurons in the mouse hippocampus.

Subsets of GABAergic neurons are surrounded by perineuronal nets (PNNs), which play a critical role in the regulation of neural plasticity and neuroprotection. Although the plant lectin Wisteria floribunda agglutinin (WFA) has been commonly used to label PNNs, WFA only detects N-acetyl-d-galactosamine on aggrecan, a member of the lectican family. In this study, we used WFA and the antibody against the core protein of aggrecan (ACAN) to investigate the molecular heterogeneity of aggrecan-based PNNs around five subclasses of parvalbumin-expressing (PV+) γ-aminobutyric acid (GABA)ergic neurons in the CA1 and CA3 regions of the mouse hippocampus. The vast majority of ACAN+ PNNs were colocalized with WFA in the stratum pyramidale, whereas a substantial population of ACAN+ PNNs lacked WFA labeling in the stratum oriens. We then defined the subclasses of PV+ neurons based on their cellular locations, molecular expression, and septal projection. Like the WFA+ PNNs, ACAN+ PNNs surrounded PV+ basket cells and bistratified cells but not axo-axonic cells. Unlike the WFA+ PNNs, ACAN+ PNNs frequently surrounded PV+ oriens-lacunosum moleculare cells and hippocampo-septal cells. Interestingly, the relative densities of GABAergic synapses were higher around PV+ neurons with ACAN+ PNNs than around those without ACAN+ PNNs. Degradation of WFA+ PNNs by chondroitinase ABC did not affect the GABAergic synaptic densities around PV+ neurons. Our findings suggest that the molecular composition of aggrecan-based PNNs around PV+ neurons may differ in a subclass-specific manner, and also might help determine the functional involvement of PNNs in the regulation of GABAergic synapses around PV+ neurons in the hippocampus. J. Comp. Neurol. 525:1234-1249, 2017. © 2016 Wiley Periodicals, Inc.

Abstract P150: Lateral Hypothalamic Leptin and Melanocortin Signaling in the Regulation of Sympathetic Nerve Activity and Blood Pressure

Obesity is associated with increased sympathetic nerve activity (SNA), which contributes to the development of hypertension. Hypothalamus plays a fundamental role in both body weight homeostasis and sympathetic outflow, but the underlying neural basis of this association remains incompletely understood. Leptin and melanocortin systems in the brain are important regulators of body weight homeostasis, SNA and blood pressure. However, the neural circuits by which leptin and melanocortin regulate SNA and blood pressure remain unclear. We have previously shown that both leptin receptor (LepR) and melanocortin 4 receptor (MC4R) are co-expressed in a unique subset of GABAergic neurons in the lateral hypothalamic area (LHA). Because the LHA is a well-known site for SNA and cardiovascular function, we hypothesized that LepR and MC4R signaling in the LHA may play an important role in SNA and blood pressure. Here we show that direct microinfusion of leptin into the LHA increases renal SNA in dose-dependent manner (% changes from baseline at 4 th hour: Vehicle -25.03 ± 7.09 %, 0.05 ug leptin 26.01 ± 9.5 %, 0.5 ug leptin 100.23 ± 26.94 %, n=5-7/group, p<0.001). Additionally, in vivo Cre/loxP system-mediated re-expression of endogenous MC4Rs in the LHA restores the blunted response of MTII-induced increase in renal SNA (Wild-type 66.67 ± 16.53 %, MC4R-null 17.65 ± 10.3 %, MC4R reactivation 48.77 ± 9.36 %, n=7-9/group, p<0.01) and elevates blood pressure in obese, but normotensive MC4R-TB mice in inactive light cycle (Wild-type 111.62 ± 4.07, MC4R-TB 115.75 ± 1.27, MC4R re-expression 125.29 ± 3014 mmHg, n=3-4/group, p<0.05) without significantly affecting body weight. Finally, optogenetic stimulation of LHA LepR-positive neurons decease blood pressure and renal SNA in conscious mice. In conclusion, our findings identify a novel brain circuit by which leptin and melanocortin signaling regulate renal SNA and blood pressure.

Glutamate Decarboxylase 67 Deficiency in a Subset of GABAergic Neurons Induces Schizophrenia-Related Phenotypes.

Decreased expression of the GABA synthetic enzyme glutamate decarboxylase 67 (GAD67) in a subset of GABAergic neurons, including parvalbumin (PV)-expressing neurons, has been observed in postmortem brain studies of schizophrenics and in animal models of schizophrenia. However, it is unclear whether and how the perturbations of GAD67-mediated GABA synthesis and signaling contribute to the pathogenesis of schizophrenia. To address this issue, we generated the mice lacking GAD67 primarily in PV neurons and characterized them with focus on schizophrenia-related parameters. We found that heterozygous mutant mice exhibited schizophrenia-related behavioral abnormalities such as deficits in prepulse inhibition, MK-801 sensitivity, and social memory. Furthermore, we observed reduced inhibitory synaptic transmission, altered properties of NMDA receptor-mediated synaptic responses in pyramidal neurons, and increased spine density in hippocampal CA1 apical dendrites, suggesting a possible link between GAD67 deficiency and disturbed glutamatergic excitatory synaptic functions in schizophrenia. Thus, our results indicate that the mice heterozygous for GAD67 deficiency primarily in PV neurons share several neurochemical and behavioral abnormalities with schizophrenia, offering a novel tool for addressing the underlying pathophysiology of schizophrenia.

Nicotine enhances inhibition of mouse vagal motor neurons by modulating excitability of premotor GABAergic neurons in the nucleus tractus solitarii.

The caudal nucleus of the solitary tract (NTS) serves as the site of the first synapse for visceral sensory inputs to the central nervous system. The NTS sends functional projections to multiple brain nuclei, with gastric-related projections primarily targeting the dorsal motor nucleus of the vagus (DMV). Previous studies have demonstrated that the majority of caudal NTS neurons that project to the DMV respond robustly to nicotine and express nicotinic acetylcholine receptors (nAChRs). However, the cytochemical identity and relationship with specific viscera of DMV-projecting, nicotine-responsive caudal NTS neurons have not been determined. The present study used transgenic mice that express enhanced green fluorescent protein (EGFP) under a GAD67 promoter in a subset of GABAergic neurons, in vivo retrograde pseudorabies viral labeling to identify gastric-related vagal complex neurons, and patch-clamp electrophysiology in acute brain stem slices to test the hypothesis that gastric-related and GABAergic inhibitory synaptic input to the DMV from the caudal NTS is under a robust modulatory control by nAChRs. Our results suggest that activation of nAChRs in the caudal NTS, but not DMV, potentiates GABAergic, but not glutamatergic, input to the DMV. Gastric-related caudal NTS and DMV neurons are directly involved in this nicotine-sensitive circuitry. Understanding the central patterns of nicotinic modulation of visceral sensory-motor circuitry may help develop therapeutic interventions to restore autonomic homeostasis in patients with autonomic impairments.

The homeodomain factorGbx1is required for locomotion and cell specification in the dorsal spinal cord

Dorsal horn neurons in the spinal cord integrate and relay sensory information to higher brain centers. These neurons are organized in specific laminae and different transcription factors are involved in their specification. The murine homeodomain Gbx1 protein is expressed in the mantle zone of the spinal cord at E12.5-13.5, correlating with the appearance of a discernable dorsal horn around E14 and eventually defining a narrow layer in the dorsal horn around perinatal stages. At postnatal stages, Gbx1 identifies a specific subpopulation of GABAergic neurons in the dorsal spinal cord. We have generated a loss of function mutation for Gbx1 and analyzed its consequences during spinal cord development. Gbx1−/− mice are viable and can reproduce as homozygous null mutants. However, the adult mutant mice display an altered gait during forward movement that specifically affects the hindlimbs. This abnormal gait was evaluated by a series of behavioral tests, indicating that locomotion is impaired, but not muscle strength or motor coordination. Molecular analysis showed that the development of the dorsal horn is not profoundly affected in Gbx1−/− mutant mice. However, analysis of terminal neuronal differentiation revealed that the proportion of GABAergic inhibitory interneurons in the superficial dorsal horn is diminished. Our study unveiled a role for Gbx1 in specifying a subset of GABAergic neurons in the dorsal horn of the spinal cord involved in the control of posterior limb movement.

Examination of ketamine-induced deficits in sensorimotor gating and spatial learning

Subanesthetic administration of the NMDA receptor antagonist ketamine has been suggested to have utility in several therapeutic domains; however, its recreational use has exceeded its therapeutic applications. Ketamine has been utilized to investigate NMDA receptor-mediated learning and memory and to model disorders such as schizophrenia. The utility of ketamine in relation to schizophrenia is based on a proposed mechanism of the disorder being associated with reduced NMDA receptor function within a subset of GABAergic neurons. The examination of ketamine with relevance to the above topics has produced valuable data; however, there exists a great deal of variability in the literature regarding dosage and timing of administration to examine ketamine-induced deficits. In the below experiments we sought to identify the minimal subanesthetic dosage and schedule of ketamine administrations that would produce behavioral deficits in multiple tasks with relevance to the above investigations. We evaluated sensorimotor gating as well as spatial learning and memory in the Morris water task utilizing different doses of ketamine. Our data indicate that an 8mg/kg subcutaneous dose of ketamine was the minimal dose to produce impairments in both sensorimotor gating and spatial learning.

GABA: A Cotransmitter Linking Leptin to Obesity Prevention

The recent surge of obesity, type II diabetes, and other obesity-relateddiseaseshasfocusedattentiononbrain mechanisms underlying the regulation of body weight. Leptinisakeyfactorlinkingbodyfattobrainmechanisms controlling food intake and energy expenditure. This hormoneisreleasedfromadipocytestocirculateatlevelsthat are approximately proportional to the levels of body fat (1).Highlevelsofleptinactonbrainfeedingcontrolmechanismsasanegativefeedbacksignaltoproducesatiety,an action produced when leptin binds to isoform B leptin receptors in specific brain regions (2). Consequently, subjects overeat and become massively obese if either endogenous leptin or its receptors are absent or ineffective. A question that has generated much interest and research is: What classes of neurons and neurotransmitters mediate leptin’s antiobesity actions? Significant insight into this question is provided by Xu et al. (3) in this issue. Their work suggests that a portion of leptin’s antiobesity effectsaremediatedbysynapticreleaseofaminobutyric acid (GABA) from the specific subset of hypothalamic GABAergic neurons that also express leptin receptors. To explore this question, they generated mice in which the vesicular GABA transporter (Vgat) gene was specifically deleted within leptin receptor-expressing neurons (i.e. LepR-Ires-Cre:Vgat flox/flox mice). The cellular impact of thismanipulationisthattheGABAergicneuronswithleptin receptors lose their ability to secrete GABA. However, they retain the ability to secrete their cotransmitters and respond to leptin. Given this manipulation, Xu et al. evaluated the impact of abolishing GABA release specifically from the subset of GABAergic neurons that also express leptin receptors. Controls for effectiveness and specificity of the gene deletions included evidence that deletion of Vgat in leptin receptor neurons: dramatically reduced Vgat mRNA expression in the arcuate nucleus, dorsomedial hypothalamus, and lateral hypothalamus (LH), the only brain regions with GABAergic neurons that express leptin receptors (4); produced little apparent change in Vgat expression in other brain regions (e.g. cortex); reduced vesicular GABA transporter immunoreactivity but left intact the leptin receptor p-STAT3 response to leptin application. The key behavioral findings were that the experimental mice exhibited mild but significant overeating, obesity, and had reduced energy expenditure as suggestedbythemildreductioninO2consumptionduringthe night phase of the light-dark cycle. The satiating effect of peripherallyinjectedleptinwasalsoblunted.Collectively,

Synaptic and intrinsic activation of respiratory GABAergic neurons in the brainstem

Respiratory sinus arrhythmia is mediated by inspiratory-evoked increases in GABAergic neurotransmission to cardiac vagal neurons (CVNs) that control heart rate. However, the mechanisms responsible for the sources and activation of the inspiratory-related GABAergic neurotransmission to CVNs are unknown. We identified a population of GABAergic neurons in the ventrolateral medulla that are activated during inspiration in a slice preparation that retains rhythmic respiratory activity. This population of inspiratory-activated GABAergic neurons receives inspiratory-related excitatory events that were blocked by the glutamatergic antagonists, NMDA and AMPA/kainate receptor antagonists AP-5 and CNQX, respectively. The nicotinic acetylcholine receptor antagonists, DHbE, 100microM and a-BTX, 100nM had no significant effect. A subset of inspiratory GABAergic neurons continue to fire in the presence of CNQX/AP-5, suggesting they may have the characteristics of a respiratory pacemaker neuron. The pacemaker cells not inhibited by CNQX were insensitive to cadmium. The results from this study demonstrate the existence of a population of GABAergic inspiratory neurons in the ventrolateral medulla that likely project to CVNs, receive increased glutamatergic neurotransmission during inspiration, and a subset of these GABAergic neurons have respiratory pacemaker properties.

GABAergic neurons expressing p75 in rat substantia innominata and nucleus basalis

In vitro findings suggested a role for the p75 neurotrophin receptor in the maturation of GABAergic neurons residing in the basal forebrain (BF), a brain area known to have p75 expression only on cholinergic neurons. We document here the presence of GABAergic neurons which express p75 in the BF in vivo. Colocalization of p75 with the cholinergic marker choline-acetyltransferase (ChAT) and/or the GABAergic marker glutamic acid decarboxylase-67 (GAD67) was investigated in the BF at birth, at two weeks, and in adulthood. A subset of GAD67 + neurons was p75 + (p75 +/GAD67 +) but ChAT − in the substantia innominata and nucleus basalis magnocellularis at birth, whereas all p75 +/GAD67 + neurons were also ChAT + from two weeks onward. These phenotypic features suggest that a subpopulation of GABAergic neurons could be sensitive to neurotrophins during brain maturation. To unravel this issue, we then pursued a functional analysis by assessing p75 expression profile, and its modulation by nerve growth factor (NGF) or brain-derived neurotrophic factor (BDNF) in primary BF cell cultures. NGF increased p75 expression exclusively in cholinergic neurons, whereas BDNF induced p75 expression only in a subset of GABAergic neurons (p75 +/GAD67 +/ChAT −) through a p75- and tyrosine-kinase-dependent mechanism. The latter findings point to a selective role of BDNF in the induction of p75 expression in BF GABAergic neurons. Altogether these results confirm the role of neurotrophins in the developing and mature circuitry of GABAergic neurons in the BF regions.

Bidirectional Plasticity Gated by Hyperpolarization Controls the Gain of Postsynaptic Firing Responses at Central Vestibular Nerve Synapses

Linking synaptic plasticity with behavioral learning requires understanding how synaptic efficacy influences postsynaptic firing in neurons whose role in behavior is understood. Here, we examine plasticity at a candidate site of motor learning: vestibular nerve synapses onto neurons that mediate reflexive movements. Pairing nerve activity with changes in postsynaptic voltage induced bidirectional synaptic plasticity in vestibular nucleus projection neurons: long-term potentiation relied on calcium-permeable AMPA receptors and postsynaptic hyperpolarization, whereas long-term depression relied on NMDA receptors and postsynaptic depolarization. Remarkably, both forms of plasticity uniformly scaled synaptic currents evoked by pulse trains, and these changes in synaptic efficacy were translated into linear increases or decreases in postsynaptic firing responses. Synapses onto local inhibitory neurons were also plastic but expressed only long-term depression. Bidirectional, linear gain control of vestibular nerve synapses onto projection neurons provides a plausible mechanism for motor learning underlying adaptation of vestibular reflexes.

Activation of GABAergic Neurons following Tooth Pulp Stimulation

The functional impact of GABA (γ-aminobutyric acid)ergic neurons in nociceptive transmission of the spinal trigeminal nucleus is not fully established. Using both the glutamic acid decarboxylase (GAD)67-green fluorescence protein (GFP) knock-in mouse and the tooth pulp stimulation model, we performed double-immunofluorescent histochemistry to determine the characteristics of GABAergic neuron activation in the spinal trigeminal nucleus. The number of Fos-positive GABAergic neuronal profiles was significantly increased 2 hrs after tooth pulp stimulation. The Fos/GFP double-labeled neurons were mainly present in superficial laminae of the spinal trigeminal subnucleus interpolaris-caudalis transition (Vi/Vc) and subnucleus caudalis (Vc) on the side ipsilateral to the stimulation. Subsequently, the number of double-labeled neurons decreased gradually and became comparable with that of the controls by 48 hrs. Our results provide direct morphological evidence that a subset of GABAergic neurons in the spinal trigeminal system was activated during tooth pulp stimulation.

SAT1, a glutamine transporter, is preferentially expressed in GABAergic neurons

Subsets of GABAergic neurons are able to maintain high frequency discharge patterns, which requires efficient replenishment of the releasable pool of GABA. Although glutamine is considered a preferred precursor of GABA, the identity of transporters involved in glutamine uptake by GABAergic neurons remains elusive. Molecular analyses revealed that SAT1 (Slc38a1) features system A characteristics with a preferential affinity for glutamine, and that SAT1 mRNA expression is associated with GABAergic neurons. By generating specific antibodies against SAT1 we show that this glutamine carrier is particularly enriched in GABAergic neurons. Cellular SAT1 distribution resembles that of GAD67, an essential GABA synthesis enzyme, suggesting that SAT1 can be involved in translocating glutamine into GABAergic neurons to facilitate inhibitory neurotransmitter generation.

Neuroanatomic relationships between the GABAergic and serotonergic systems in the developing human medulla

γ-Amino butyric (GABA) critically influences serotonergic (5-HT) neurons in the raphé and extra-raphé of the medulla oblongata. In this study we hypothesize that there are marked changes in the developmental profile of markers of the human medullary GABAergic system relative to the 5-HT system in early life. We used single- and double-label immunocytochemistry and tissue receptor autoradiography in 15 human medullae from fetal and infant cases ranging from 15 gestational weeks to 10 postnatal months, and compared our findings with an extensive 5-HT-related database in our laboratory. In the raphé obscurus, we identified two subsets of GABAergic neurons using glutamic acid decarboxylase (GAD65/67) immunostaining: one comprised of small, round neurons; the other, medium, spindle-shaped neurons. In three term medullae cases, positive immunofluorescent neurons for both tryptophan hydroxylase and GAD65/67 were counted within the raphé obscurus. This revealed that approximately 6% of the total neurons counted in this nucleus expressed both GAD65/67 and TPOH suggesting co-production of GABA by a subset of 5-HT neurons. The distribution of GABA A binding was ubiquitous across medullary nuclei, with highest binding in the raphé obscurus. GABA A receptor subtypes α1 and α3 were expressed by 5-HT neurons, indicating the site of interaction of GABA with 5-HT neurons. These receptor subtypes and KCC2, a major chloride transporter, were differentially expressed across early development, from midgestation (20 weeks) and thereafter. The developmental profile of GABAergic markers changed dramatically relative to the 5-HT markers. These data provide baseline information for medullary studies of human pediatric disorders, such as sudden infant death syndrome.

A ventral tegmental CRF–glutamate–dopamine interaction in addiction

Stress-induced reinstatement of cocaine-seeking is blocked by antagonists for the stress-related neurohormone corticotropin-releasing factor (CRF). One site of this action is the ventral tegmental area (VTA), where mild footshock stress causes CRF release, glutamate release, and dopaminergic activation in cocaine-experienced but not cocaine-naive animals. Infusion of CRF into VTA has similar effects to footshock in cocaine-experienced animals but fails to cause significant VTA glutamate release or dopaminergic activation in cocaine-naive animals. The reinstatement, glutamate release, and dopamine release are prevented by VTA infusions of CRF-receptor 2 (CRF-R2) but not CRF-R1 antagonists. Reinstatement is triggered by some but not all CRF-R2 agonists and some but not all CRF-R1 agonists; the common denominator of the effective agonists is that they bind to the CRF-binding protein (CRF-BP), which appears to be essential for the behavioral and VTA effects of stress and CRF in cocaine-experienced animals. In situ hybridization reveals mRNA for CRF-R1 and CRF-BP but not CRF-R2 in a subset of VTA dopamine neurons. Electron microscopy reveals primarily asymmetric synapses between a subset of VTA terminals containing glutamate and CRF and a subset of VTA dopaminergic neurons and primarily symmetric synapses between a subset of CRF terminals that do not contain glutamate and a subset of GABAergic neurons in VTA. Thus, a complex and not yet fully understood interaction of CRF, glutamate, and the mesocorticolimbic dopamine system is established by experience with cocaine, and this alteration appears to contribute importantly to the transition from casual to compulsive cocaine-seeking.

Vesicular glutamate transporters in the normal and pathological central nervous system of rodent and human

Event Abstract Back to Event Vesicular glutamate transporters in the normal and pathological central nervous system of rodent and human B. Amilhon1, 2, C. Gras1, 2, E. M. Lepicard1, 2, O. Poirel1, 2, L. E. Trudeau3, L. Lanfumay4, B. Gasnier5, B. Giros1, 2 and Salah E. Mestikawy1, 2* 1 Universite Pierre et Marie Curie, INSERM U513, France 2 McGill University, Department of Psychiatry, Canada 3 Université de Montréal, Department of Pharmacology, Canada 4 INSERM, U677, Neuropsychopharmacology, France 5 Université Paris , Centre National de la Recherche Scientifique, France Glutamate is the primary excitatory neurotransmitter in the mammalian central nervous system (CNS). Before its exocytotic release, proton-driven carriers accumulate glutamate into synaptic vesicles. This function is fulfilled by three vesicular glutamate transporters (named VGLUT1-3) that are structurally and functionally highly conserved. VGLUT1-3 has complementary distributions in the rat brain. VGLUT1 is expressed by glutamatergic neurons of the cerebral and cerebellar cortices, the hippocampus and the thalamus. VGLUT2 is present in excitatory neurons throughout the diencephalon and the brainstem. VGLUT3 has a very restricted and completely unexpected localization. This subtype is found in neurons known to release other classical neurotransmitters, such as cholinergic interneurons of the striatum and the nucleus accumbens, subsets of GABAergic neurons in the cortex and hippocampus, and serotoninergic raphe neurons. Using subtype specific antiserums, we have inspected VGLUT3 distribution within 5-HT terminals. We found that VGLUT3 unravels an unsuspected level of complexity of these modulatory fibres. Using a mouse line lacking VGLUT3 (VGLUT3-KO) we established that glutamate regulates acetylcholine vesicular filling and release at the level of synaptic vesicles. This new and unexpected mechanism was designed as "Vesicular Synergy". These observations open numerous perspectives with regards to VGLUT3 functions in non-glutamatergic neurotransmission. In particular, VGLUT3 and vesicular synergy may have many compelling physiological and pharmacological implications for serotoninergic transmission and mood disorders that await further investigations. Keywords: Brain, Glutamate, knock-out, vesicular glutamate transporter, VGLUT3 Conference: 3rd Mediterranean Conference of Neuroscience , Alexandria, Egypt, 13 Dec - 16 Dec, 2009. Presentation Type: Oral Presentation Topic: Symposium 14 – Serotonin neurobiology: new vistas Citation: Amilhon B, Gras C, Lepicard EM, Poirel O, Trudeau LE, Lanfumay L, Gasnier B, Giros B and Mestikawy SE (2009). Vesicular glutamate transporters in the normal and pathological central nervous system of rodent and human. Front. Neurosci. Conference Abstract: 3rd Mediterranean Conference of Neuroscience . doi: 10.3389/conf.neuro.01.2009.16.052 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 19 Nov 2009; Published Online: 19 Nov 2009. * Correspondence: Salah E Mestikawy, Universite Pierre et Marie Curie, INSERM U513, Paris, France, salah.elmestikawy@mcgill.ca Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers B. Amilhon C. Gras E. M Lepicard O. Poirel L. E Trudeau L. Lanfumay B. Gasnier B. Giros Salah E Mestikawy Google B. Amilhon C. Gras E. M Lepicard O. Poirel L. E Trudeau L. Lanfumay B. Gasnier B. Giros Salah E Mestikawy Google Scholar B. Amilhon C. Gras E. M Lepicard O. Poirel L. E Trudeau L. Lanfumay B. Gasnier B. Giros Salah E Mestikawy PubMed B. Amilhon C. Gras E. M Lepicard O. Poirel L. E Trudeau L. Lanfumay B. Gasnier B. Giros Salah E Mestikawy Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Glutamatergic cerebellar granule neurons synthesize and secrete reelin in vitro

In the postnatal forebrain, the extracellular matrix protein reelin is expressed and secreted by subsets of GABAergic neurons, whereas in the cerebellum reelin is detected in glutamatergic cells of the granule cell layer. Thus, various regions of the postnatal brain present different patterns of reelin expression, whose significance remains unknown. We combined immunocytochemical and pharmacological approaches to characterize the phenotypic and temporal profiles of reelin expression in dissociated cultures of cerebellar granule neurons. A single type of reelin immunoreactivity, identified by a punctate labelling, was present in the somata of the majority of neurons. This immunoreactivity was observed throughout maturation and was exclusively present in glutamatergic neurons expressing the vesicular glutamate transporter 1. Neurons containing the reelin receptors apolipoprotein E receptor 2 (Apoer2) and very low-density lipoprotein receptor (Vldlr) represented about 80% of cerebellar neurons. The vast majority of reelin-positive neurons coexpressed Apoer2, suggesting that reelin immunoreactivity resulted in part from receptor-bound reelin. Inhibition of protein synthesis with cycloheximide completely abolished reelin immunoreactivity. In contrast, blocking protein secretion with brefeldin A did not affect the proportion of punctate neurons but revealed a subpopulation of neurons characterized by a solid reelin staining. These data show for the first time that a homogeneous population of glutamatergic neurons can synthesize and secrete reelin in cerebellar granule cells in vitro.