Amygdala gene expression of NMDA and GABAA receptors in patients with mesial temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is the most common form of partial epilepsy and affects 40% of the patients. Seizures arising from the mesial temporal lobe structures (i.e., amygdala and hippocampus) are common, whereas neocortical seizures are rare. In recent years, many studies aimed to identify the pattern of gene expression of neurotransmitters involved in molecular mechanisms of epilepsy. We used real-time PCR to quantify the expression of GABAA (subunits a1, beta 1, beta 2) and NMDA (subunits NR1, NR2A, and NR2B) receptor genes in amygdalae of 27 patients with TLE and 14 amygdalae from autopsy controls. The NR1 subunit was increased in patients with epilepsy when compared with controls. No differences were found in expression of NMDA subunits NR2A and NR2B or in a1, beta 1, and beta 2 subunits of GABAA receptors. Our results suggest that the NR1 subunit of NMDA receptors is involved in the amygdala hyperexcitability in some of the patients with TLE. (C) 2010 Wiley Periodicals, Inc., Inc.

Activity differentially regulates the surface expression of synaptic AMPA and NMDA glutamate receptors

Distinct subtypes of glutamate receptors often are colocalized at individual excitatory synapses in the mammalian brain yet appear to subserve distinct functions. To address whether neuronal activity may differentially regulate the surface expression at synapses of two specific subtypes of ionotropic glutamate receptors we epitope-tagged an AMPA (α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid) receptor subunit (GluR1) and an NMDA (N-methyl-d-aspartate) receptor subunit (NR1) on their extracellular termini and expressed these proteins in cultured hippocampal neurons using recombinant adenoviruses. Both receptor subtypes were appropriately targeted to the synaptic plasma membrane as defined by colocalization with the synaptic vesicle protein synaptophysin. Increasing activity in the network of cultured cells by prolonged blockade of inhibitory synapses with the γ-aminobutyric acid type A receptor antagonist picrotoxin caused an activity-dependent and NMDA receptor-dependent decrease in surface expression of GluR1, but not NR1, at synapses. Consistent with this observation identical treatment of noninfected cultures decreased the contribution of endogenous AMPA receptors to synaptic currents relative to endogenous NMDA receptors. These results indicate that neuronal activity can differentially regulate the surface expression of AMPA and NMDA receptors at individual synapses.

Mobility of NMDA autoreceptors but not postsynaptic receptors at glutamate synapses in the rat entorhinal cortex

NMDA receptors (NMDAr) are known to undergo recycling and lateral diffusion in postsynaptic spines and dendrites. However, NMDAr are also present as autoreceptors on glutamate terminals, where they act to facilitate glutamate release, but it is not known whether these receptors are also mobile. We have used functional pharmacological approaches to examine whether NMDA receptors at excitatory synapses in the rat entorhinal cortex are mobile at either postsynaptic sites or in presynaptic terminals. When NMDAr-mediated evoked EPSCs (eEPSCs) were blocked by MK-801, they showed no evidence of recovery when the irreversible blocker was removed, suggesting that postsynaptic NMDAr were relatively stably anchored at these synapses. However, using frequency-dependent facilitation of AMPA receptor (AMPAr)-mediated eEPSCs as a reporter of presynaptic NMDAr activity, we found that when facilitation was blocked with MK-801 there was a rapid (similar to 30-40 min) anomalous recovery upon removal of the antagonist. This was not observed when global NMDAr blockade was induced by combined perfusion with MK-801 and NMDA. Anomalous recovery was accompanied by an increase in frequency of spontaneous EPSCs, and a variable increase in frequency-facilitation. Following recovery from blockade of presynaptic NMDAr with a competitive antagonist, frequency-dependent facilitation of AMPAr-mediated eEPSCs was also transiently enhanced. Finally, an increase in frequency of miniature EPSCs induced by NMDA was succeeded by a persistent decrease. Our data provide the first evidence for mobility of NMDAr in the presynaptic terminals, and may point to a role of this process in activity-dependent control of glutamate release.

Targeting glucocorticoid receptors that promote resilience in the treatment of addiction

There is strong evidence to suggest that the combination of alcohol and chronic repetitive stress leads to long-lasting effects on brain function, specifically areas associated with stress, motivation and decision-making such as the amygdala, nucleus accumbens and prefrontal cortex. Alcohol and stress together facilitate the imprinting of long-lasting memories. The molecular mechanisms and circuits involved are being studied but are not fully understood. Current evidence suggests that corticosterone (animals) or cortisol (humans), in addition to direct transcriptional effects on the genome, can directly regulate pre- and postsynaptic synaptic transmission through membrane bound glucocorticoid receptors (GR). Indeed, corticosterone-sensitive synaptic receptors may be critical sites for stress regulation of synaptic responses. Direct modulation of synaptic transmission by corticosterone may contribute to the regulation of synaptic plasticity and memory during stress (Johnson et al., 2005; Prager et al., 2010). Specifically, previous data has shown that long term alcohol (1) increases the expression of NR2Bcontaining NMDA receptors at glutamate synapses, (2) changes receptor density, and (3) changes morphology of dendritic spines (Prendergast and Mulholland; 2012). During alcohol withdrawal these changes are associated with increased glucocorticoid signalling and increased neuronal excitability. It has therefore been proposed that these synapse changes lead to the anxiety and alcohol craving associated with withdrawal (Prendergast and Mulholland; 2012). My lab is targeting this receptor system and the amygdala in order to understand the effect of combining alcohol and stress on these pathways. Lastly, we are testing GR specific compounds as potential new medications to promote the development of resilience to developing addiction.

NMDA modulates oligodendrocyte differentiation of subventricular zone cells through PKC activation

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Inibição do receptor de glutamato do tipo NMDA em um modelo de hipóxia-isquemia prenatal: avaliação morfofuncional do cerebelo

Lesões sistêmicas peri e pré-natais alteram o desenvolvimento do SNC, levando a problemas cognitivos e motores em crianças que podem perdurar por toda a vida. Um tipo particular de lesão é a hipóxia-isquemia (HI), caracterizada pela interrupção momentânea ou permanente do fluxo sanguíneo. Um dos mecanismos propostos para as lesões decorrentes da HI é a excitotoxicidade glutamatérgica. O uso de inibidores da neurotransmissão glutamatérgica tem sido estudados em diversos modelos de HI. Neste trabalho, avaliamos os efeitos morfofuncionais da administração de um antagonista não-competitivo do receptor de glutamato NMDA sobre o desenvolvimento do cerebelo. Ratas no 18 dia de gestação foram anestesiadas, os cornos uterinos expostos e as 4 artérias uterinas obstruídas por 45 minutos (Grupo H). Animais controle tiveram os úteros expostos, sem a obstrução (Grupo S). Após a cirurgia a gestação prosseguiu. Somente animais nascidos a termo foram utilizados. Um dia após o nascimento, metade de cada ninhada foi designada para receber MK801, 0,3mg/kg/dia, (grupos SM e HM) e a outra metade recebeu solução salina (grupos SS e HS), por 5 dias. Após anestesia e perfusão-fixação com paraformaldeído 4% aos 9, 23, 30 e 60 dias pós-natais, cortes parassagitais do cerebelo foram obtidos em criótomo e submetidos à imunohistoquímica para calbindina, GFAP, GLAST, PDGFRα e MBP. A partir de 45 dias de vida, os animais foram testados em vários de testes comportamentais: labirinto em cruz elevado (LCE), campo vazado (CV), ROTAROD, teste de caminhada sobre barras (ladder test) e teste do comprimento da passada (stride length). Aos 9 dias, a espessura da árvore dendrítica era menor nos animais SM, HS/HM, demonstrando efeitos deletérios tanto do MK801 quanto da HI. Menor número de células PDGFRα+ foi observado nos animais HS/HM, sem efeitos da administração de MK801. Aos 23 dias, maior número de células PDGFRα+ foi observado nos animais HM comparado aos outros 3 grupos, indicando efeito neuroprotetor do MK801. Nessa idade, menor número de fibras mielinizadas (MBP+) foi observada nos animais HS, e a administração de MK801 parece reverter estes efeitos. Aos 9 dias a distribuição de GLAST estava alterada nos animais HS, com os efeitos da HI parcialmente revertidos pelo MK801. Não foram observados efeitos da HI ou do MK801 sobre comportamentos relacionados a ansiedade pelo LCE, assim como na latência de queda no ROTAROD. HI piora a performance motora no ladder test. No teste do CV, não observamos efeitos da HI sobre a busca por novidade assim como sobre a atividade locomotora espontânea. No entanto, MK801 diminui comportamentos de autolimpeza e a atividade locomotora espontânea. Menor variação das passadas foi observada em decorrência da administração de MK801 no stride length, com nenhum efeito da HI. Nossos resultados demonstram que a inibição do receptor NMDA tem um efeito neuroprotetor sobre os progenitores de oligodendrócitos e mielinização, provavelmente pela manutenção da capacidade proliferativa por um período maior. A atividade do receptor NMDA exerce importante papel na diferenciação das células de Purkinje, assim como na distribuição do transportador GLAST, corroborando a importância deste receptor na gênese das lesões causadas pela HI.

Papel do bloqueio dos receptores NMDA e da ativação dos receptores GABAA na manifestação dos déficits neurocomportamentais decorrentes da exposição ao etanol durante o período equivalente ao terceiro trimestre de gestação

A exposição gestacional ao etanol produz um amplo espectro de defeitos neurocomportamentais que podem persistir ao longo da vida. Dentre os distúrbios mais comumente observados estão o transtorno do déficit de atenção e hiperatividade (TDAH) e os déficits de aprendizado e memória. Apesar da grande quantidade de estudos, os mecanismos envolvidos com a manifestação destes transtornos permanecem pouco conhecidos. Estudos em roedores vêm demonstrando que o período equivalente ao terceiro trimestre de gestação é critico para o aparecimento destas alterações comportamentais. Durante este período, que é caracterizado por intensa sinaptogênese, a neurotoxicidade do etanol vem sendo atribuída ao bloqueio dos receptores glutamatérgicos do tipo N-metil-D-aspartato (NMDA) e hiperativação dos receptores do ácido gama-aminobutírico do subtipo A (GABAA). Tendo em vista que ao longo do desenvolvimento estes receptores diferem em relação a função e distribuição espaço-temporal, neste estudo avaliamos a contribuição relativa do bloqueio dos receptores NMDA e hiperativação dos receptores GABAA durante o período equivalente ao terceiro trimestre de gestação para a manifestação da hiperatividade locomotora e para os distúrbios de aprendizado e memória de camundongos pré-púberes. Para tanto, este estudo foi realizado em duas etapas. Na primeira, investigamos os efeitos da exposição isolada ao bloqueador NMDA MK801 (MK) e ao agonista GABAA muscimol (MU). Para tanto, em dias alternados do segundo dia pós-natal (PN2) a PN8, os animais receberam uma injeção intraperitoneal de Salina (SAL), MK nas doses de 0,1, 0,3 ou 0,5 mg/kg ou de MU nas doses de 0,1 0,3 ou 0,5 mg/kg. Na segunda etapa investigamos os efeitos da administração simultânea de MK (0,1mg/kg) e MU (doses 0,02, 0,1 ou 0,5 mg/kg). Em PN25, a atividade locomotora foi automaticamente avaliada por 15 min no teste de campo aberto. Em PN31 e PN32, o aprendizado e memória foi avaliado no teste da esquiva passiva inibitória. Em relação aos resultados da exposição isolada a cada uma das drogas, apenas o tratamento com MK promoveu um aumento dose dependente na atividade locomotora. No teste da esquiva passiva inibitória, os animais expostos as maiores doses de MK e MU apresentaram déficits de aprendizado e memória. Em relação aos resultados da exposição combinada de MK e MU, não foram observadas diferenças significativas entre os grupos na atividade locomotora. Na esquiva passiva inibitória, a administração simultânea de MK e MU, em doses que administradas isoladamente não tiveram efeito, promoveu prejuízos de aprendizado e memória. Nossos resultados sugerem que, enquanto a hiperatividade locomotora está associada apenas com o bloqueio dos receptores NMDA, os déficits de aprendizado e memória podem ser produto de uma ação sinergista do etanol nos dois receptores.

Long-term depression in rat CA1-subicular synapses depends on the G-protein coupled mACh receptors

The subiculum, which is the primary target of CA1 pyramidal neurons and sending efferent fibres to many brain regions, serves as a hippocampal interface in the neural information processes between hippocampal formation and neocortex. Long-term depression (LTD) is extensively studied in the hippocampus, but not at the CA1-subicular synaptic transmission. Using whole-cell EPSC recordings in the brain slices of young rats, we demonstrated that the pairing protocols of low frequency stimulation (LFS) at 3 Hz and postsynaptic depolarization of -50 mVelicited a reliable LTD in the subiculum. The LTD did not cause the changes of the paired-pulse ratio of EPSC. Furthermore, it did not depend on either NMDA receptors or voltage-gated calcium channels (VGCCs). Bath application of the G-protein coupled muscarinic acetylcholine receptors (mAChRs) antagonists, atropine or scopolamine, blocked the LTD, suggesting that mAChRs are involved in the LTD. It was also completely blocked by either the Ca2+ chelator BAPTA or the G-protein inhibitor GDP-beta-S in the intracellular solution. This type of LTD in the subiculum may play a particular role in the neural information processing between the hippocampus and neocortex. (c) 2005 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.

Specific targeting of pro-death NMDA receptor signals with differing reliance on the NR2B PDZ ligand.

NMDA receptors (NMDARs) mediate ischemic brain damage, for which interactions between the C termini of NR2 subunits and PDZ domain proteins within the NMDAR signaling complex (NSC) are emerging therapeutic targets. However, expression of NMDARs in a non-neuronal context, lacking many NSC components, can still induce cell death. Moreover, it is unclear whether targeting the NSC will impair NMDAR-dependent prosurvival and plasticity signaling. We show that the NMDAR can promote death signaling independently of the NR2 PDZ ligand, when expressed in non-neuronal cells lacking PSD-95 and neuronal nitric oxide synthase (nNOS), key PDZ proteins that mediate neuronal NMDAR excitotoxicity. However, in a non-neuronal context, the NMDAR promotes cell death solely via c-Jun N-terminal protein kinase (JNK), whereas NMDAR-dependent cortical neuronal death is promoted by both JNK and p38. NMDAR-dependent pro-death signaling via p38 relies on neuronal context, although death signaling by JNK, triggered by mitochondrial reactive oxygen species production, does not. NMDAR-dependent p38 activation in neurons is triggered by submembranous Ca(2+), and is disrupted by NOS inhibitors and also a peptide mimicking the NR2B PDZ ligand (TAT-NR2B9c). TAT-NR2B9c reduced excitotoxic neuronal death and p38-mediated ischemic damage, without impairing an NMDAR-dependent plasticity model or prosurvival signaling to CREB or Akt. TAT-NR2B9c did not inhibit JNK activation, and synergized with JNK inhibitors to ameliorate severe excitotoxic neuronal loss in vitro and ischemic cortical damage in vivo. Thus, NMDAR-activated signals comprise pro-death pathways with differing requirements for PDZ protein interactions. These signals are amenable to selective inhibition, while sparing synaptic plasticity and prosurvival signaling.

Mécanismes de plasticité synaptique dans l’amygdale lors de la réactivation de la mémoire de peur auditive chez le rat : interaction dynamique des récepteurs NMDA et AMPA

La plasticité synaptique est une propriété indispensable à l’acquisition de la mémoire chez toutes les espèces étudiées, des invertébrés aux primates. La formation d’une mémoire débute par une phase de plasticité qui inclut une restructuration synaptique ; ensuite elle se poursuit par la consolidation de ces modifications, contribuant à la mémoire à long terme. Certaines mémoires redeviennent malléables lorsqu’elles sont rappelées. La trace mnésique entre alors dans une nouvelle de phase de plasticité, au cours de laquelle certaines composantes de la mémoire peuvent être mises à jour, puis reconsolidées. L’objectif de la présente thèse est d’étudier les mécanismes cellulaires et moléculaires qui sont activés lors du rappel d’une mémoire. Nous avons utilisé un modèle de conditionnement Pavlovien, combiné à l’administration d’agents pharmacologiques et à l’analyse quantitative de marqueurs de plasticité synaptique, afin d’étudier la dynamique de la mémoire de peur auditive chez des rats Sprague Dawley. La circuiterie neuronale et les mécanismes associatifs impliqués dans la neurobiologie de cette mémoire sont bien caractérisés, en particulier le rôle des récepteurs glutamatergiques de type NMDA et AMPA dans la plasticité synaptique et la consolidation. Nos résultats démontrent que le retour de la trace mnésique à un état de labilité nécessite l’activation des récepteurs NMDA dans l’amygdale baso-latérale à l’instant même du rappel, alors que les récepteurs AMPA sont requis pour l’expression comportementale de la réponse de peur conditionnée. D’autre part, les résultats identifient le rappel comme une phase bien plus dynamique que présumée, et suggèrent que l’expression de la peur conditionnée mette en jeu la régulation du trafic des récepteurs AMPA par les récepteurs NMDA. Le présent travail espère contribuer à la compréhension de la neurobiologie fondamentale de la mémoire. De plus, il propose une intégration des résultats aux modèles animaux d’étude des troubles psychologiques conséquents aux mémoires traumatiques chez l’humain, tels que les phobies et les syndromes de stress post-traumatiques.

Étude du rôle des récepteurs NMDA du mésencéphale ventral dans la récompense induite par la stimulation électrique du mésencéphale postérieur chez le rongeur.

La voie dopaminergique mésolimbique qui prend son origine dans le mésencéphale ventral et qui projette vers des régions rostrales du système limbique fait partie du substrat nerveux qui contrôle la récompense et les comportements motivés. Il a été suggéré qu’un signal de récompense est produit lorsque le patron de décharge des neurones dopaminergiques passe d’un mode tonique à un mode phasique, une transition qui est initiée par l’action du glutamate aux récepteurs N-Méthyl-D-aspartate (NMDA). Étant donné qu’une altération du système de récompense est souvent associée à des anomalies cliniques telles que l’addiction compulsive et à des troubles émotionnels tels que l’anhédonie, nous avons étudié le rôle des récepteurs NMDA dans la récompense induite par la stimulation électrique intracérébrale. Puisque les récepteurs NMDA sont composés de sous-unités distinctes, GluN1, GluN2 et GluN3, nous avons étudié le rôle de deux sous-unités qui sont présentes dans le mésencéphale ventral : GluN2A et GluN2B. Les résultats montrent que des injections mésencéphaliques de R-CPP et de PPPA, des antagonistes préférentiels aux sous-unités GluN2A/B, ont produit une augmentation dose-dépendante de l’effet de récompense, un effet qui était, à certains temps après les injections, accompagné d’une augmentation du nombre de réponses maximales. Ces effets n’ont pas été observés après l’injection d’une large gamme de doses de Ro04-5595, un antagoniste des sous-unités GluN2B. Ces résultats suggèrent que le glutamate mésencéphalique exerce une modulation négative sur le circuit de récompense, un effet dû à son action au niveau des récepteurs NMDA composés des sous-unités GluN2A.

Bone marrow cells differentiation to neurons in the rat brain using Serotonin and GABA:Their role on glutamate receptors, IP3, cAMP and cGMP functional regulation in unilateral Parkinsonism induced by 6-hydroxydopamine

Parkinson's disease is a chronic progressive neurodegenerative movement disorder characterized by a profound and selective loss of nigrostriatal dopaminergic neurons. Our findings demonstrated that glutamatergic system is impaired during PD. The evaluations of these damages have important implications in understanding the molecular mechanism underlying motor, cognitive and memory deficits in PD. Our results showed a significant increase of glutamate content in the brain regions of 6- OHDA infused rat compared to control. This increased glutamate content caused an increase in glutamatergic and NMDA receptors function. Glutamate receptor subtypes- NMDAR1, NMDA2B and mGluR5 have differential regulatory role in different brain regions during PD. The second messenger studies confirmed that the changes in the receptor levels alter the IP3, cAMP and cGMP content. The alteration in the second messengers level increased the expression of pro-apoptotic factors - Bax and TNF-α, intercellular protein - α-synuclein and reduced the expression of transcription factor - CREB. These neurofunctional variations are the key contributors to motor and cognitive abnormalities associated with PD. Nestin and GFAP expression study confirmed that 5-HT and GABA induced the differentiation and proliferation of the BMC to neurons and glial cells in the SNpc of rats. We also observed that activated astrocytes are playing a crucial role in the proliferation of transplanted BMC which makes them significant for stem cell-based therapy. Our molecular and behavioural results showed that 5-HT and GABA along with BMC potentiates a restorative effect by reversing the alterations in glutamate receptor binding, gene expression and behaviour abnormality that occur during PD. The therapeutic significance in Parkinson’s disease is of prominence.

A role for hippocampal PSA-NCAM and NMDA-NR2B receptor function in flavonoid-induced spatial memory improvements in young rats

The increase in incidence and prevalence of neurodegenerative diseases highlights the need for a more comprehensive understanding of how food components may affect neural systems. In particular, flavonoids have been recognized as promising agents capable of influencing different aspects of synaptic plasticity resulting in improvements in memory and learning in both animals and humans. Our previous studies highlight the efficacy of flavonoids in reversing memory impairments in aged rats, yet little is known about the effects of these compounds in healthy animals, particularly with respect to the molecular mechanisms by which flavonoids might alter the underlying synaptic modifications responsible for behavioral changes. We demonstrate that a 3-week intervention with two dietary doses of flavonoids (Dose I: 8.7 mg/day and Dose II: 17.4 mg/day) facilitates spatial memory acquisition and consolidation (24 recall) (p < 0.05) in young healthy rats. We show for the first time that these behavioral improvements are linked to increased levels in the polysialylated form of the neural adhesion molecule (PSA-NCAM) in the dentate gyrus (DG) of the hippocampus, which is known to be required for the establishment of durable memories. We observed parallel increases in hippocampal NMDA receptors containing the NR2B subunit for both 8.7 mg/day (p < 0.05) and 17.4 mg/day (p < 0.001) doses, suggesting an enhancement of glutamate signaling following flavonoid intervention. This is further strengthened by the simultaneous modulation of hippocampal ERK/CREB/BDNF signaling and the activation of the Akt/mTOR/Arc pathway, which are crucial in inducing changes in the strength of hippocampal synaptic connections that underlie learning. Collectively, the present data supports a new role for PSA-NCAM and NMDA-NR2B receptor on flavonoid-induced improvements in learning and memory, contributing further to the growing body of evidence suggesting beneficial effects of flavonoids in cognition and brain health.

Anxiogenic-like effects induced by NMDA receptor activation are prevented by inhibition of neuronal nitric oxide synthase in the periaqueductal gray in mice

Glutamate-NMDA (N-methyl-D-aspartate) receptor activation within the periaqueductal gray (PAG) leads to antinociceptive, autonomic and behavioral responses characterized as the fear reaction. We have recently demonstrated that the vigorous defensive-like behaviors (e.g. jumping and running) and antinociception induced by intra-PAG injection of N-methyl-D-aspartate (NMDA) were completely blocked by prior infusion of N(omega)-propyl-L-arginine (NPLA), a specific neuronal nitric oxide synthesis (nNOS) enzyme inhibitor, into the same midbrain structure. It remains unclear however, whether the inhibition of nNOS within the mouse PAG changes the anxiety-like behavior per se or the effects of the inhibition of nNOS depend on the suppression of downstream of glutamate-NMDA receptor activation. This study investigated whether intra-PAG infusion of NPLA (i) attenuates anxiety in the elevated plus-maze (EPM) and (ii) antagonizes the anxiogenic-like effects induced by intra-PAG injection of NMDA. Test sessions were videotaped and subsequently scored for conventional indices of anxiety (percentage of open arm entries and percentage of open arm time) and locomotor activity (closed arm entries). Results showed that intra-PAG infusions of NPLA (0.2, 0.4 or 0.8 nmol/0.1 mu l) did not alter significantly any behavioral response in the EPM when compared to control group (Experiment 1). Intra-PAG infusion of NMDA (0 and 0.02 nmol/0.1 mu l; a dose that does not provoke vigorous defensive behaviors per se in mice) significantly reduced open arm exploration, confirming an anxiogenic-like effect (Experiment 2). When injected into the PAG 10 min prior local NMDA injection (0.02 nmol/0.1 mu l), NPLA (0.4 nmol/0.1 mu l) was able to revert the anxiogenic-like effect of glutamate-NMDA receptor activation. Neither intra-PAG infusion of NMDA nor NPLA altered closed arm entries, a widely used measure of locomotor activity in the EPM. These results suggest that intra-PAG nitric oxide synthesis does not play a role on anxiety-like behavior elicited during EPM exposure; however its synthesis is important for the proaversive effects produced by activation of glutamate-NMDA receptors located within this limbic midbrain structure. (C) 2008 Elsevier B.V. All rights reserved.