RESUMO
Chemical inhibition and nitrergic stimulation of the left and right medial prefrontal cortex (L and RmPFC), respectively, provoke anxiety in mice. Moreover, LmPFC inhibition immediately followed by a single social defeat stress (SDS) led to anxiogenesis in mice exposed to the elevated plus maze (EPM) 24â¯h later. Given that glutamate NMDA (N-methyl-D-aspartate) receptors are densely present in the mPFC, we investigated (i) the time course of LmPFC inhibitionâ¯+â¯SDS-induced anxiogenesis and (ii) the effects of intra-RmPFC injection of AP-7 (a NMDA receptor antagonist) on this long-lasting anxiety. Male Swiss mice received intra-LmPFC injection of CoCl2 (1â¯mM) and 10â¯min later were subjected to a single SDS episode and then (i) exposed to the EPM 2, 5, or 10 days later or (ii) 2 days later, received intra-RmPFC injection of AP-7 (0.05â¯nmol) and were exposed to the EPM to observe the percentage of open arm entries and time (%OE; %OT) and frequency of closed arm entries (CE). Dorsal but not ventral LmPFC inhibitionâ¯+â¯SDS reduced open arm exploration 2, 5, and 10 days later relative to that of saline-treated or non-defeated mice. Moreover, this effect is not due to locomotor impairment as assessed using the general activity. Intra-RmPFC AP-7 injection 2 days after LmPFC inhibitionâ¯+â¯SDS prevented this type of anxiogenesis. These results suggest that the integrity of the LmPFC is important for mice to properly cope with SDS, and that NMDA receptor blockade in the RmPFC facilitates resilience to SDS-induced anxiogenesis in mice.
Assuntos
Ansiedade , Comportamento Animal , Antagonistas de Aminoácidos Excitatórios/farmacologia , Aprendizagem em Labirinto , Córtex Pré-Frontal/efeitos dos fármacos , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Derrota Social , Estresse Psicológico/complicações , 2-Amino-5-fosfonovalerato/análogos & derivados , 2-Amino-5-fosfonovalerato/farmacocinética , Adaptação Psicológica/efeitos dos fármacos , Adaptação Psicológica/fisiologia , Animais , Ansiedade/etiologia , Ansiedade/fisiopatologia , Ansiedade/prevenção & controle , Comportamento Animal/efeitos dos fármacos , Comportamento Animal/fisiologia , Antagonistas de Aminoácidos Excitatórios/farmacocinética , Lateralidade Funcional/fisiologia , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Aprendizagem em Labirinto/fisiologia , CamundongosRESUMO
Exposure of rats to an environment with low O2 levels evokes a panic-like escape behavior and recruits the dorsal periaqueductal gray (dPAG), which is considered to be a key region in the pathophysiology of panic disorder. The neurochemical basis of this response is, however, currently unknown. We here investigated the role played by nitric oxide (NO) within the dPAG in mediation of the escape reaction induced by hypoxia exposure. The results showed that exposure of male Wistar rats to 7% O2 increased nitrite levels, a NO metabolite, in the dPAG but not in the amygdala or hypothalamus. Nitrite levels in the dPAG were correlated with the number of escape attempts during the hypoxia challenge. Injections of the NO synthesis inhibitor NPA, the NO-scavenger c- PTIO, or the NMDA receptor antagonist AP-7 into the dorsolateral column of the periaqueductal gray (dlPAG) inhibited escape expression during hypoxia, without affecting the rats' locomotion. Intra-dlPAG administration of c-PTIO had no effect on the escape response evoked by the elevated-T maze, a defensive behavior that has also been associated with panic attacks. Altogether, our results suggest that NO plays a critical role in mediation of the panic-like defensive response evoked by exposure to low O2 concentrations.
Assuntos
Reação de Fuga/fisiologia , Hipóxia/fisiopatologia , Óxido Nítrico/fisiologia , Pânico/fisiologia , Substância Cinzenta Periaquedutal/fisiologia , 2-Amino-5-fosfonovalerato/administração & dosagem , 2-Amino-5-fosfonovalerato/análogos & derivados , 2-Amino-5-fosfonovalerato/farmacologia , Tonsila do Cerebelo/metabolismo , Animais , Arginina/administração & dosagem , Arginina/análogos & derivados , Arginina/farmacologia , Reação de Fuga/efeitos dos fármacos , Hipotálamo/metabolismo , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Microinjeções , Atividade Motora/efeitos dos fármacos , Nitritos/metabolismo , Substância Cinzenta Periaquedutal/metabolismo , RatosRESUMO
The transient receptor potential vanilloid 1 (TRPV1) can modulate stress-related behaviours, thus representing an interesting target for new antidepressant drugs. TRPV1 can trigger glutamate release and nitric oxide synthesis in the brain, mechanisms also involved in the neurobiology of depression. However, it is not known if these mechanisms are involved in TRPV1-induced behavioural effects. Therefore, the aim of this study was to verify if the antidepressant-like effect induced by a TRPV1 antagonist in mice submitted to the forced swimming test (FST) would be facilitated by combined treatment with neuronal nitric oxide synthase (nNOS) inhibition and N-methyl-D-aspartate (NMDA) blockade. Male Swiss mice were given (intracerebroventricular) injections of capsazepine (CPZ) (TRPV1 antagonist - 0.05/0.1/0.3/0.6 nmol/µl), and AP7 (NMDA antagonist - 1/3/10 nmol/µl) or N-propyl-L-arginine (NPA, nNOS inhibitor - 0.001/0.01/0.1 nmol/µl), and 10 min later, submitted to an open field test, and immediately afterwards, to the FST. An additional group received coadministration of CPZ and AP7 or CPZ and NPA, in subeffective doses. The results demonstrated that CPZ (0.1 nmol/µl), AP7 (3 nmol/µl) and NPA (0.01/0.1 nmol/µl) induced antidepressant-like effects. Moreover, coadministration of subeffective doses of CPZ and AP7 or CPZ and NPA induced significant antidepressant-like effects. Altogether, the data indicate that blockade of TRPV1 receptors by CPZ induces antidepressant-like effects and that both nNOS inhibition and NMDA blockade facilitate CPZ effects in the FST.
Assuntos
Antidepressivos/uso terapêutico , Capsaicina/análogos & derivados , Depressão/tratamento farmacológico , Ácido Glutâmico/metabolismo , Óxido Nítrico/metabolismo , Natação/psicologia , 2-Amino-5-fosfonovalerato/análogos & derivados , 2-Amino-5-fosfonovalerato/farmacologia , Animais , Apomorfina/análogos & derivados , Apomorfina/farmacologia , Arginina/farmacologia , Capsaicina/uso terapêutico , GMP Cíclico/metabolismo , Depressão/metabolismo , Depressão/fisiopatologia , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Vias de Administração de Medicamentos , Inibidores Enzimáticos/farmacologia , Comportamento Exploratório/efeitos dos fármacos , Masculino , Microinjeções , Nitroprussiato/metabolismo , Ratos , Receptores de N-Metil-D-Aspartato/metabolismo , Estatísticas não ParamétricasRESUMO
BACKGROUND: An excitatory imbalance in the hypothalamus of rodents caused by local chemical stimulation elicits fear-related defensive reactions such as escape and freezing. In addition, these panic attack-like defensive reactions induced by hypothalamic neurons may cause antinociception. However, there is a shortage of studies showing the participation of the anterior hypothalamic nucleus in these adaptive defensive mechanisms. Nitric oxide (NO) donors have been shown to evoke fear-related defensive responses when microinjected into paralimbic and limbic structures, and this excitatory neuromodulation can recruit the glutamatergic system. AIMS: The aim of this work was to investigate the influence of the glutamatergic system in the nitrergic effects on fear-related defensive responses organised by anterior hypothalamic neurons. METHODS: The present study evaluates the effects of the molsidomine active metabolite SIN-1 NO donor administered into the anterior hypothalamus (AH) of mice at different concentrations (75, 150 and 300 nmol/0.1 µL). Then, we investigated the effects of pre-treatment of the AH with AP-7 (an N-methyl-d-aspartate (NMDA) receptor-selective antagonist; 0.02, 0.2 and 2 nmol/0.1 µL) on the behavioural and antinociceptive effects provoked by AH chemical stimulation with SIN-1 microinjections. RESULTS: The 300 nmol dose of SIN-1 was the most effective at causing panic-like defensive behaviours followed by a significant antinociceptive response. In addition, both of these effects were attenuated or inhibited by AH pre-treatment with AP-7. CONCLUSIONS: These findings suggest that the panicogenic and antinociceptive effects evoked by intra-AH microinjections of SIN-1 depend on NMDA receptor activation.
Assuntos
Medo/efeitos dos fármacos , Molsidomina/análogos & derivados , Doadores de Óxido Nítrico/administração & dosagem , Pânico/efeitos dos fármacos , 2-Amino-5-fosfonovalerato/administração & dosagem , 2-Amino-5-fosfonovalerato/análogos & derivados , 2-Amino-5-fosfonovalerato/farmacologia , Animais , Comportamento Animal/efeitos dos fármacos , Relação Dose-Resposta a Droga , Hipotálamo Anterior/efeitos dos fármacos , Hipotálamo Anterior/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Microinjeções , Molsidomina/administração & dosagem , Molsidomina/farmacologia , Doadores de Óxido Nítrico/farmacologia , Receptores de N-Metil-D-Aspartato/efeitos dos fármacos , Receptores de N-Metil-D-Aspartato/metabolismoRESUMO
The dorsal hippocampus (DH) is a structure of the limbic system that is involved in emotional, learning and memory processes. There is evidence indicating that the DH modulates cardiovascular correlates of behavioral responses to stressful stimuli. Acute restraint stress (RS) is an unavoidable stress situation that evokes marked and sustained autonomic changes, which are characterized by elevated blood pressure (BP), intense heart rate (HR) increase and a decrease in cutaneous temperature. In the present study, we investigated the involvement of an N-methyl-D-aspartate (NMDA) glutamate receptor/nitric oxide (NO) pathway of the DH in the modulation of autonomic (arterial BP, HR and tail skin temperature) responses evoked by RS in rats. Bilateral microinjection of the NMDA receptor antagonist AP-7 (10 nmol/500 nL) into the DH attenuated RS-evoked autonomic responses. Moreover, RS evoked an increase in the content of NO2/NO3 in the DH, which are products of the spontaneous oxidation of NO under physiological conditions that can provide an indirect measurement of NO production. Bilateral microinjection of N-propyl-L-arginine (0.1 nmol/500 nL; N-propyl, a neuronal NO synthase (nNOS) inhibitor) or carboxy-PTIO (2 nmol/500 nL; c-PTIO, an NO scavenger) into the DH also attenuated autonomic responses evoked by RS. Therefore, our findings suggest that a glutamatergic system present in the DH is involved in the autonomic modulation during RS, acting via NMDA receptors and nNOS activation. Furthermore, the present results suggest that NMDA receptor/nNO activation has a facilitatory influence on RS-evoked autonomic responses.
Assuntos
Hipocampo/fisiopatologia , Óxido Nítrico/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Estresse Psicológico/fisiopatologia , 2-Amino-5-fosfonovalerato/análogos & derivados , 2-Amino-5-fosfonovalerato/farmacologia , Animais , Pressão Arterial/efeitos dos fármacos , Antagonistas de Aminoácidos Excitatórios/farmacologia , Sequestradores de Radicais Livres/farmacologia , Frequência Cardíaca/efeitos dos fármacos , Masculino , Nitratos/metabolismo , Óxido Nítrico Sintase Tipo I/antagonistas & inibidores , Óxido Nítrico Sintase Tipo I/metabolismo , Nitritos/metabolismo , Ratos , Ratos Wistar , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Restrição Física , Transdução de Sinais/efeitos dos fármacos , Temperatura Cutânea/efeitos dos fármacos , Estresse Psicológico/tratamento farmacológico , CaudaRESUMO
RATIONALE: The endocannabinoid and endovanniloid anandamide (AEA) exerts biphasic effects when injected into the dorsolateral periaqueductal grey (dlPAG) in rats submitted to threatening situations. Whereas lower doses of AEA induce anxiolytic-like effects by activating cannabinoid CB1 receptors, no effects are observed with higher doses, possibly due to the simultaneous activation of transient receptor potential vanilloid type 1 (TRPV1) receptors. This activation would facilitate glutamatergic neurotransmission. OBJECTIVE: Considering that the blockade of TRPV1 or NMDA receptors in the dlPAG induces anxiolytic-like effects, we tested the hypothesis that facilitation of glutamate transmission through TRPV1 is responsible for the lack of anxiolytic-like effect observed with high AEA doses. METHODS: Male Wistar rats with a unilateral cannula aimed at the dlPAG received injections of an ineffective dose of AP7 (an NMDA antagonist, 1 nmol) or capsazepine (CPZ, a TRPV1 antagonist, 10 nmol), followed by a high dose of AEA (50 and 200 pmol) and were exposed to the elevated plus maze (EPM) or the Vogel conflict test (VCT). RESULTS: AP7, CPZ, or AEA did not induce any significant effects when administered alone. However, AP7 or CPZ prior to AEA significantly increased the percentage of entries and time spent in the open arms of EPM and the number of punished licks in the VCT suggesting an anxiolytic-like effect. CONCLUSIONS: These results suggest that the lack of anxiolytic-like effect of higher AEA doses is due to facilitation of glutamate release in the dlPAG, probably via activation of TRPV1 receptors in this structure.
Assuntos
Ácidos Araquidônicos/farmacologia , Endocanabinoides/farmacologia , Alcamidas Poli-Insaturadas/farmacologia , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Canais de Cátion TRPV/antagonistas & inibidores , 2-Amino-5-fosfonovalerato/análogos & derivados , 2-Amino-5-fosfonovalerato/farmacologia , Animais , Ácidos Araquidônicos/administração & dosagem , Agonistas de Receptores de Canabinoides/administração & dosagem , Agonistas de Receptores de Canabinoides/farmacologia , Capsaicina/análogos & derivados , Capsaicina/farmacologia , Relação Dose-Resposta a Droga , Endocanabinoides/administração & dosagem , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Substância Cinzenta Periaquedutal/efeitos dos fármacos , Alcamidas Poli-Insaturadas/administração & dosagem , Ratos , Ratos WistarRESUMO
The inferior colliculus (IC), a midbrain structure that processes acoustic information of aversive nature, is distinguished from other auditory nuclei in the brainstem by its connections with structures of the motor system. Recent evidence relating the IC to motor behavior shows that glutamate-mediated mechanisms in the neural circuits at the IC level modulate haloperidol-induced catalepsy. It has been shown that N(G)-nitro-L-arginine (L-NOARG), inhibitor of enzyme nitric oxide synthase (NOS), can induce catalepsy after intraperitoneal (ip), intracerebroventricular or intrastriatal administration. The present study examined whether the catalepsy induced by L-NOARG (ip) can be influenced by collicular glutamatergic mechanisms and if a NO-dependent neural substrate into the IC plays a role in this immobility state. L-NOARG-induced catalepsy was challenged with prior intracollicular microinjections of glutamate NMDA receptor antagonists, AP7 (20 or 40 nmol/0.5 µl), or of the NMDA receptor agonist N-methyl-D-aspartate (NMDA, 30 nmol/0.5 µl). Catalepsy was evaluated by positioning both forepaws of the rats on an elevated horizontal wooden bar and recording the time for which the animal maintained this position. The results showed that intracollicular microinjection of AP7 previous to systemic injections of L-NOARG (90 mg/kg) significantly attenuated the catalepsy. Conversely, intracollicular microinjection of NMDA increased the time of catalepsy when administered 10 min before systemic L-NOARG (10 or 45 mg/kg). The microinjection of L-NOARG (50 or 100 nmol) directly into the IC was not able to induce catalepsy. These findings suggest that glutamate-mediated mechanisms in the neural circuits of the IC modulate L-NOARG-induced catalepsy and participate in the regulation of motor activity.
Assuntos
Catalepsia/induzido quimicamente , Catalepsia/patologia , Inibidores Enzimáticos/toxicidade , Colículos Inferiores/metabolismo , Nitroarginina/toxicidade , Receptores de N-Metil-D-Aspartato/metabolismo , 2-Amino-5-fosfonovalerato/administração & dosagem , 2-Amino-5-fosfonovalerato/análogos & derivados , Animais , Catalepsia/prevenção & controle , Relação Dose-Resposta a Droga , Esquema de Medicação , Interações Medicamentosas , Antagonistas de Aminoácidos Excitatórios/administração & dosagem , Colículos Inferiores/efeitos dos fármacos , Masculino , Microinjeções , N-Metilaspartato/administração & dosagem , Ratos , Ratos Wistar , Estatísticas não Paramétricas , Fatores de TempoRESUMO
Long-term memory (LTM) consolidation requires the synthesis of plasticity-related proteins (PRPs). In addition, we have shown recently that LTM formation also requires the setting of a "learning tag" able to capture those PRPs. Weak training, which results only in short-term memory, can set a tag to use PRPs derived from a temporal-spatial closely related event to promote LTM formation. Here, we studied the involvement of glutamatergic, dopaminergic, and noradrenergic inputs on the setting of an inhibitory avoidance (IA) learning tag and the synthesis of PRPs. Rats explored an open field (PRP donor) followed by weak (tag inducer) or strong (tag inducer plus PRP donor) IA training. Throughout pharmacological interventions around open-field and/or IA sessions, we found that hippocampal dopamine D1/D5- and ß-adrenergic receptors are specifically required to induce PRP synthesis. Moreover, activation of the glutamatergic NMDA receptors is required for setting the learning tags, and this machinery further required α-Ca(2+)/calmodulin-dependent protein kinase II and PKA but not ERK1/2 activity. Together, the present findings emphasize an essential role of the induction of PRPs and learning tags for LTM formation. The existence of only the PRP or the tag was insufficient for stabilization of the mnemonic trace.
Assuntos
Aprendizagem da Esquiva/fisiologia , Memória de Longo Prazo/fisiologia , Memória de Curto Prazo/fisiologia , Plasticidade Neuronal/fisiologia , 1-(5-Isoquinolinasulfonil)-2-Metilpiperazina/análogos & derivados , 1-(5-Isoquinolinasulfonil)-2-Metilpiperazina/farmacologia , 2-Amino-5-fosfonovalerato/análogos & derivados , 2-Amino-5-fosfonovalerato/farmacologia , Antagonistas Adrenérgicos beta/farmacologia , Animais , Benzazepinas/farmacologia , Região CA1 Hipocampal/metabolismo , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/antagonistas & inibidores , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/metabolismo , Dobutamina/farmacologia , Inibidores Enzimáticos/farmacologia , Antagonistas de Aminoácidos Excitatórios/farmacologia , Comportamento Exploratório/fisiologia , Masculino , Memória de Longo Prazo/efeitos dos fármacos , Memória de Curto Prazo/efeitos dos fármacos , Propranolol/farmacologia , Ratos , Ratos Wistar , Receptores Adrenérgicos beta/metabolismo , Receptores de Dopamina D1/antagonistas & inibidores , Receptores de Dopamina D1/metabolismo , Receptores de Dopamina D5/antagonistas & inibidores , Receptores de Dopamina D5/metabolismo , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Receptores de N-Metil-D-Aspartato/metabolismoRESUMO
The present study investigated the role of the glutathione system in seizures induced by diphenyl diselenide (PhSe)(2) (50 mg/kg) in rat pups (post natal day, 12-14). Reduced glutathione (GSH) (300 nmol/site; i.c.v.), administered 20 min before (PhSe)(2), abolished the appearance of seizures, protected against the inhibition of catalase and δ-aminolevulinic dehydratase (δ-ALA-D) activities and increased glutathione peroxidase (GPx) activity induced by (PhSe)(2). Administration of l-buthionine sulfoximine (BSO, a GSH-depleting compound) (3.2 µmol/site; i.c.v.) 24h before (PhSe)(2) increased the percentage (42-100%) of rat pups which had seizure episodes, reduced the onset for the first convulsive episode. In addition, BSO increased thiobarbituric acid reactive species (TBARS) levels and decreased GSH content, catalase, δ-ALA-D and Na(+), K(+)-ATPase activities. Treatment with sub effective doses of GSH (10 nmol/site) and d-2-amino-7-phosphonoheptanoic acid (AP-7, an antagonist of the glutamate site at the NMDA receptor; 5mg/kg, i.p.) abolished the appearance of seizures induced by (PhSe)(2) in rat pups. Sub effective doses of GSH and kynurenic acid (an antagonist of strychnine-insensitive glycine site at the NMDA receptor; 40 mg/kg, i.p.) were also able in abolishing the appearance of seizures induced by (PhSe)(2). In conclusion, administration of GSH protected against seizure episodes induced by (PhSe)(2) in rat pups by reducing oxidative stress and, at least in part, by acting as an antagonist of glutamate and glycine modulatory sites in the NMDA receptor.
Assuntos
Glutationa/fisiologia , Convulsões/induzido quimicamente , 2-Amino-5-fosfonovalerato/análogos & derivados , 2-Amino-5-fosfonovalerato/farmacologia , Animais , Animais Recém-Nascidos , Derivados de Benzeno/toxicidade , Butionina Sulfoximina/farmacologia , Catalase/metabolismo , Feminino , Glutationa/farmacologia , Glutationa Peroxidase/metabolismo , Ácido Cinurênico/farmacologia , Masculino , Compostos Organosselênicos/toxicidade , Estresse Oxidativo , Sintase do Porfobilinogênio/metabolismo , Ratos , Ratos Wistar , Receptores de N-Metil-D-Aspartato/agonistas , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Receptores de N-Metil-D-Aspartato/metabolismo , ATPase Trocadora de Sódio-Potássio/metabolismo , Substâncias Reativas com Ácido Tiobarbitúrico/metabolismoRESUMO
LHRH release from hypothalamus is influenced by the neurotransmitter glutamate that acts, among others, on NMDA receptors present in LHRH neurons. On the other hand, the neurosteroid allopregnanolone can modulate the activity of specific neurotransmitter receptors and affect neurotransmitter release. We examined the role of allopregnanolone on in vitro LHRH and glutamate release from mediobasal hypothalamus and anterior preoptic area of ovariectomized rats with estrogen and progesterone replacement. Moreover, we evaluated whether the neurosteroid might act through modulation of NMDA receptors. Allopregnanolone induced an increase in LHRH release. This effect was reversed when the NMDA receptors were blocked by the NMDA antagonist 2-amino-7-phosphonoheptanoic acid (AP-7) indicating that this neurosteroid would interact with NMDA receptors. Moreover allopregnanolone induced an augment in K(+) evoked [(3)H]-glutamate release from mediobasal hypothalamus-anterior preoptic area explants and this effect was also reversed when NMDA receptors were blocked with AP-7. These results suggest an important physiologic function of allopregnanolone on the regulation of neuroendocrine function in female adult rats. Not only appears to be involved in enhancing LHRH release through modulation of NMDA receptors but also in the release of glutamate which is critical in the control of LHRH release.
Assuntos
Ácido Glutâmico/metabolismo , Hormônio Liberador de Gonadotropina/metabolismo , Hipotálamo/metabolismo , Neurotransmissores/farmacologia , Pregnanolona/farmacologia , Receptores de N-Metil-D-Aspartato/efeitos dos fármacos , 2-Amino-5-fosfonovalerato/análogos & derivados , 2-Amino-5-fosfonovalerato/farmacologia , Animais , Terapia de Reposição de Estrogênios , Feminino , Hipotálamo/efeitos dos fármacos , Técnicas In Vitro , Modelos Animais , N-Metilaspartato/farmacologia , Ovariectomia , Área Pré-Óptica/efeitos dos fármacos , Área Pré-Óptica/metabolismo , Ratos , Ratos Sprague-Dawley , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Receptores de N-Metil-D-Aspartato/fisiologiaRESUMO
The dorsal premammillary nucleus (PMd) is a hypothalamic structure that plays a pivotal role in the processing of predatory threats. Lesions of this nucleus virtually eliminate the expression of defensive responses to predator exposure. However, little is known about the neurotransmitters responsible for these behavioral responses. Since PMd neurons express ionotropic glutamate receptors and exposure to predators have been shown to activate nitric oxide (NO) producing cells in this region, the aim of this study was to verify the involvement of glutamate and NO-mediated neurotransmission in defensive reactions modulated by the PMd. We tested in male Wistar rats the hypothesis that intra-PMd injection of the NMDA receptor antagonist, AP7, or the NO synthase inhibitor, N-propyl-L-arginine (NP), would attenuate behavioral responses induced by cat exposure. Our results showed that both AP7 and NP significantly attenuated the behavioral responses induced by the live cat. These results suggest that the NMDA/NO pathway plays an important role in the behavioral responses mediated by the PMd.
Assuntos
Mecanismos de Defesa , Medo , Corpos Mamilares/fisiologia , N-Metilaspartato/metabolismo , Óxido Nítrico/metabolismo , 2-Amino-5-fosfonovalerato/análogos & derivados , 2-Amino-5-fosfonovalerato/farmacologia , Animais , Arginina/farmacologia , Comportamento Animal/efeitos dos fármacos , Comportamento Animal/fisiologia , Gatos , Antagonistas de Aminoácidos Excitatórios/farmacologia , Medo/efeitos dos fármacos , Reação de Congelamento Cataléptica/efeitos dos fármacos , Locomoção/efeitos dos fármacos , Locomoção/fisiologia , Masculino , Corpos Mamilares/efeitos dos fármacos , Ratos , Ratos Wistar , Estatísticas não ParamétricasRESUMO
The inferior colliculus (IC) is primarily involved in the processing of auditory information, but it is distinguished from other auditory nuclei in the brainstem by its connections with structures of the motor system. Functional evidence relating the IC to motor behavior derives from experiments showing that activation of the IC by electrical stimulation or excitatory amino acid microinjection causes freezing, escape-like behavior, and immobility. However, the nature of this immobility is still unclear. The present study examined the influence of excitatory amino acid-mediated mechanisms in the IC on the catalepsy induced by the dopamine receptor blocker haloperidol administered systemically (1 or 0.5 mg/kg) in rats. Haloperidol-induced catalepsy was challenged with prior intracollicular microinjections of glutamate NMDA receptor antagonists, MK-801 (15 or 30 mmol/0.5 microl) and AP7 (10 or 20 nmol/0.5 microl), or of the NMDA receptor agonist N-methyl-d-aspartate (NMDA, 20 or 30 nmol/0.5 microl). The results showed that intracollicular microinjection of MK-801 and AP7 previous to systemic injections of haloperidol significantly attenuated the catalepsy, as indicated by a reduced latency to step down from a horizontal bar. Accordingly, intracollicular microinjection of NMDA increased the latency to step down the bar. These findings suggest that glutamate-mediated mechanisms in the neural circuits at the IC level influence haloperidol-induced catalepsy and participate in the regulation of motor activity.
Assuntos
Catalepsia/induzido quimicamente , Catalepsia/patologia , Ácido Glutâmico/metabolismo , Haloperidol , Colículos Inferiores/fisiopatologia , Receptores de N-Metil-D-Aspartato/fisiologia , 2-Amino-5-fosfonovalerato/análogos & derivados , 2-Amino-5-fosfonovalerato/farmacologia , Animais , Maleato de Dizocilpina/farmacologia , Relação Dose-Resposta a Droga , Interações Medicamentosas , Agonistas de Aminoácidos Excitatórios/farmacologia , Antagonistas de Aminoácidos Excitatórios/farmacologia , Colículos Inferiores/efeitos dos fármacos , Masculino , Microinjeções/métodos , Atividade Motora/efeitos dos fármacos , N-Metilaspartato/farmacologia , Ratos , Ratos Wistar , Estatísticas não Paramétricas , Transmissão Sináptica/efeitos dos fármacosRESUMO
Innate fear stimulus induces activation of neurons containing the neuronal nitric oxide synthase enzyme (nNOS) in defensive-related brain regions such as the dorsolateral periaqueductal gray (dlPAG). Intra-dlPAG administration of nitric oxide synthase (NOS) inhibitors and glutamate antagonists induce anxiolytic-like responses. We investigated the involvement of nitric oxide (NO) and glutamate neurotransmission in defensive reactions modulated by dlPAG. We tested if intra-dlPAG injections of the selective nNOS inhibitor, N-propyl-L-arginine (NP), or the glutamate antagonist, AP7 (2-amino-7-phosphonoheptanoic acid), would attenuate behavioral responses and cellular activation induced by predator exposure (cat). Fos-like immunoreactivity (FLI) was used as a marker of neuronal functional activation, whereas nNOS immunohistochemistry was used to identify NOS neurons. Cat exposure induced fear responses and an increase of FLI in the dlPAG and dorsal premammillary nucleus (PMd). NP and AP7 attenuated the cat-induced behavioral responses. Whereas NP tended to attenuate FLI in the dlPAG, AP7 induced a significant reduction in cellular activation of this region. The latter drug, however, increased FLI and double-labeled cells in the PMd. Cellular activation of this region was significantly correlated with time spent near the cat (r = 0.7597 and 0.6057 for FLI and double-labeled cells). These results suggest that glutamate/NO-mediated neurotransmission in the dlPAG plays an important role in responses elicit by predator exposure. Blocking these neurotransmitter systems in this brain area impairs defensive responses. The longer time spent near the predator that follows AP7 effect could lead to an increased cellular activation of the PMd, a more rostral brain area that has also been related to defensive responses.
Assuntos
Medo/efeitos dos fármacos , Óxido Nítrico Sintase Tipo I/antagonistas & inibidores , Substância Cinzenta Periaquedutal/efeitos dos fármacos , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , 2-Amino-5-fosfonovalerato/análogos & derivados , 2-Amino-5-fosfonovalerato/farmacologia , Animais , Arginina/análogos & derivados , Arginina/farmacologia , Comportamento Animal/efeitos dos fármacos , Comportamento Animal/fisiologia , Inibidores Enzimáticos/farmacologia , Antagonistas de Aminoácidos Excitatórios/farmacologia , Medo/fisiologia , Masculino , Óxido Nítrico/metabolismo , Proteínas Proto-Oncogênicas c-fos/metabolismo , Ratos , Ratos Wistar , Transmissão Sináptica/efeitos dos fármacos , Transmissão Sináptica/fisiologia , Fatores de TempoRESUMO
Effects of blocking N-methyl-D-aspartic acid (NMDA) and non-NMDA glutamatergic receptors on performance in the hole board test was studied in male rats bilaterally cannulated into the nucleus accumbens (Acc). Rats, divided into 5 groups, received either 1 microl injections of saline, (+/-) 2-amino-7-phosphonoheptanoic acid (AP-7) (0.5 or 1 microg) or 2,3-dioxo-6-nitro-1,2,3,4,tetrahydrobenzo-(f)quinoxaline-7-sulphonamide disodium (NBQX, 0.5 or 1 microg) 10 min before testing. An increase by AP-7 was observed in ambulatory movements (0.5 microg; p < 0.05), non-ambulatory movements and number of movements (1 microg; p < 0.05); sniffing and total exploration (1 microg; p < 0.01). When holes were considered in order from the first to the fifth by the number of explorations, the most visited holes (first and second) of the AP-7 group were significantly higher than the corresponding holes of saline group (p < 0.05 for 0.5 microg and p < 0.001 for 1 microg). When the second hole was compared with the first of his group, a difference was only observed in the AP-7 1 microg group (p < 0.001). Increasing differences between the other holes and the first were observed by drug treatment. At molecular level, it was observed that AP-7 induced an increase of the coat protein AP-2 expression in Acc, but not AP-180 neither the synaptic protein synaptophysin. The increase of AP-2 was also observed in the medial prefrontal cortex by the action of AP-7 but not NBQX. We conclude that NMDA glutamatergic blockade might induce an activation of the endocytic machinery into the Acc, leading to stereotypies and perseverations, lacking cortical intentional direction.
Assuntos
Endocitose/fisiologia , Antagonistas de Aminoácidos Excitatórios/farmacologia , Núcleo Accumbens/metabolismo , Córtex Pré-Frontal/metabolismo , 2-Amino-5-fosfonovalerato/análogos & derivados , 2-Amino-5-fosfonovalerato/farmacologia , Complexo 2 de Proteínas Adaptadoras/efeitos dos fármacos , Complexo 2 de Proteínas Adaptadoras/metabolismo , Animais , Comportamento Animal/efeitos dos fármacos , Comportamento Animal/fisiologia , Endocitose/efeitos dos fármacos , Glutamina/metabolismo , Immunoblotting , Masculino , Atividade Motora/efeitos dos fármacos , Atividade Motora/fisiologia , Núcleo Accumbens/efeitos dos fármacos , Córtex Pré-Frontal/efeitos dos fármacos , Quinoxalinas/farmacologia , Ratos , Receptores de N-Metil-D-Aspartato/antagonistas & inibidoresRESUMO
It is well established that the most persistent sign of withdrawal from chronic benzodiazepine use in humans is anxiety. In contrast to other types of drugs of abuse, the emergence of this anxiety does not seem to be linked directly to alterations in the levels of dopamine in the mesolimbic system. Some studies have proposed that fear-like behaviors elicited by benzodiazepine withdrawal could be the result either of alterations in the sensitivity of GABAA receptors or in the neuronal hyperexcitability that results from neuroadaptative responses to chronic treatment, probably mediated by glutamate. The increased fear-like behaviors induced by benzodiazepine withdrawal are similar to the defense reaction displayed by animals exposed to dangerous situations or submitted to electrical or chemical stimulation of the dorsal periaqueductal gray (dPAG), a key structure of the brain aversive system. However, the involvement of the dPAG in drug abuse has been investigated only in the context of the physical effects of drug dependence. Thus, in this study we investigated the effects of injections into the dPAG of the glutamic acid diethyl ester (GDEE) and 2-amino-7-phosphonoheptanoate (AP-7) (AMPA-kainate and NMDA receptors antagonists, respectively) on fear-like behaviors promoted by benzodiazepine withdrawal in rats submitted to aversive events (foot-shocks) immediately before chronic diazepam administration in a conditioning place-preference paradigm, using a light-dark box. Our results showed that inhibition of the glutamatergic neurotransmission in the dPAG reduces the consequence of the diazepam withdrawal in rats, implicating the excitatory amino acids of the dPAG in the modulation of the aversive state induced by benzodiazepine drugs withdrawal.
Assuntos
Diazepam/efeitos adversos , Antagonistas de Aminoácidos Excitatórios/farmacologia , Hipnóticos e Sedativos/efeitos adversos , Substância Cinzenta Periaquedutal/efeitos dos fármacos , Receptores de AMPA/antagonistas & inibidores , Receptores de Ácido Caínico/antagonistas & inibidores , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Síndrome de Abstinência a Substâncias/prevenção & controle , Síndrome de Abstinência a Substâncias/psicologia , 2-Amino-5-fosfonovalerato/análogos & derivados , 2-Amino-5-fosfonovalerato/farmacologia , Animais , Condicionamento Operante/efeitos dos fármacos , Eletrochoque , Ratos , Ratos Wistar , Reforço Psicológico , Transmissão Sináptica/efeitos dos fármacosRESUMO
The involvement of the dorsolateral periaqueductal gray in the regulation of fear-related behaviors such as escape and freezing is well established. It is still a matter of investigation, however, whether this midbrain area may have a relevant role in the modulation of more subtle defensive responses associated with anxiety such as risk assessment and inhibitory avoidance. By stimulating N-methyl-D-aspartic acid glutamate receptors located in the dorsolateral periaqueductal gray with its prototypical agonist N-methyl-D-aspartic acid (50 pmol), we report here an increase in both risk assessment and inhibitory avoidance behaviors of male Wistar rats tested in the elevated T-maze. These results are indicative of an anxiogenic-like effect. The selective N-methyl-D-aspartic acid receptor antagonist DL-2-amino-7-phosphonoheptanoic acid (2.0 and 4.0 nmol) had the opposite effect on both defensive tasks. Pretreatment with an ineffective dose of DL-2-amino-7-phosphonoheptanoic acid (1.0 nmol) prevented the N-methyl-D-aspartic acid anxiogenic-like effect. At the dose range of DL-2-amino-7-phosphonoheptanoic acid and/or N-methyl-D-aspartic acid tested, neither the escape response from one of the elevated T-maze open arms nor the general exploratory activity as assessed in the open-field test was affected. The present results suggest that the dorsolateral periaqueductal gray column is also involved in the regulation of defensive behaviors related to anxiety, and N-methyl-D-aspartic acid glutamate receptors are recruited for this action.
Assuntos
Ansiedade/tratamento farmacológico , Ansiedade/psicologia , Medo/efeitos dos fármacos , Medo/psicologia , Substância Cinzenta Periaquedutal/fisiologia , Receptores de N-Metil-D-Aspartato/efeitos dos fármacos , Assunção de Riscos , 2-Amino-5-fosfonovalerato/administração & dosagem , 2-Amino-5-fosfonovalerato/análogos & derivados , 2-Amino-5-fosfonovalerato/farmacologia , Animais , Anticonvulsivantes/farmacologia , Etossuximida/farmacologia , Agonistas de Aminoácidos Excitatórios/administração & dosagem , Agonistas de Aminoácidos Excitatórios/farmacologia , Antagonistas de Aminoácidos Excitatórios/administração & dosagem , Antagonistas de Aminoácidos Excitatórios/farmacologia , Comportamento Exploratório/efeitos dos fármacos , Hipocampo/fisiologia , Masculino , Microinjeções , N-Metilaspartato/administração & dosagem , N-Metilaspartato/farmacologia , Ratos , Ratos WistarRESUMO
Several neurotransmitters, including GABA, serotonin, glutamate, and cholecystokinin, modulate defensive behaviors in the dorsolateral periaqueductal gray (dlPAG). Although both glutamate and cholecystokinin have been shown to facilitate these behaviors, a possible interaction between them remains to be examined. The present study investigates whether activation or antagonism of N-methyl-D-aspartic acid (NMDA) glutamate and cholecystokinin 2 (CCK(2)) receptors located in the dlPAG would interact in animals tested in the elevated T-maze. The effect of the NMDA (50 pmol) was evaluated in rats pretreated with the CCK(2) receptor antagonist LY225910 (0.05 nmol). In addition, the effect of the CCK(2) receptor agonist CCK-4 (0.08 nmol) was evaluated in rats pretreated with the NMDA receptor antagonist AP-7 (1.0 nmol). Intra-dlPAG injection of NMDA increased risk assessment and inhibitory avoidance behaviors. This NMDA anxiogenic-like effect was unaltered by the pretreatment with LY225910. Similarly, the shortening of escape latencies induced by CCK-4 was unaffected by AP-7. No drug changed the general exploratory activity as assessed in the open-field. These results, showing that the activation of dlPAG NMDA or CCK(2) receptors facilitate anxiety- and fear-related behaviors, further implicate glutamate and cholecystokinin-mediated neurotransmission in this midbrain area on modulation of defensive behaviors. However, the regulatory action of these two excitatory neurotransmitters seems to be exerted through independent mechanisms.
Assuntos
Comportamento Animal/efeitos dos fármacos , Agonistas de Aminoácidos Excitatórios/farmacologia , N-Metilaspartato/farmacologia , Substância Cinzenta Periaquedutal/metabolismo , Receptor de Colecistocinina B/antagonistas & inibidores , Transdução de Sinais/efeitos dos fármacos , 2-Amino-5-fosfonovalerato/análogos & derivados , 2-Amino-5-fosfonovalerato/farmacologia , Animais , Relação Dose-Resposta a Droga , Fármacos Gastrointestinais/farmacologia , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Quinazolinonas/farmacologia , Ratos , Ratos Wistar , Receptor de Colecistocinina B/metabolismo , Tetragastrina/farmacologiaRESUMO
The present study investigated if NOS positive neurons localized in regions related to defensive reactions are activated after exposure to an innate fear stimulus (a live cat). Male Wistar rats were exposed to a live or a toy cat for 10 min and 2h later had their brains removed and processed for c-Fos immunohistochemistry (a marker of neuronal functional activation) and NADPH-diaphorase (NADPH-d; used to detect the presence of NOS neurons) histochemistry. Cat exposure induced a small (11%) to moderate (50%) significant increase in the percentage of double-stained cells (c-Fos+NADPH-d positive neurons) in the anteromedial bed nucleus of stria terminalis (BSTMA), medial amygdala (MeA), parvocellular paraventricular (pPVN), lateral (LH) and dorsal premammillary (PMd) hypothalamic nuclei, dorsolateral periaqueductal grey (dlPAG) and dorsal raphe nucleus (DRN). This increase was attenuated in the PMd, DRN and dlPAG by i.c.v. injection of AP7 (5 nmol/2 microl), an NMDA receptor antagonist. The drug increased the percentage of time the rats remained close to the cat in the observation box. The results suggest that exposure to a live predator activates neurons containing NOS in brain areas related to defensive reactions. They also indicate that this effect probably involves activation of NMDA glutamate receptors.
Assuntos
Encéfalo/fisiologia , Gatos , Medo/fisiologia , Óxido Nítrico Sintase/fisiologia , Proteínas Proto-Oncogênicas c-fos/fisiologia , Meio Social , 2-Amino-5-fosfonovalerato/análogos & derivados , 2-Amino-5-fosfonovalerato/farmacologia , Animais , Nível de Alerta/efeitos dos fármacos , Nível de Alerta/fisiologia , Encéfalo/anatomia & histologia , Depressão Química , Antagonistas de Aminoácidos Excitatórios/farmacologia , Medo/efeitos dos fármacos , Técnicas Imunoenzimáticas , Masculino , Ratos , Ratos Wistar , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Receptores de N-Metil-D-Aspartato/fisiologiaRESUMO
The ventral portion of the medial prefrontal cortex (vMPFC) is involved in the modulation of the parasympathetic component of the baroreflex. In the present study, we verified the effect of blockade of vMPFC glutamatergic receptors and nitric oxide synthases (NOS) on the parasympathetic component of baroreflex in awake rats. Bilateral microinjection of the non-selective ionotropic glutamate antagonist kynurenic acid (KYN) into the vMPFC caused a shift of the threshold of reflex bradycardia toward higher pressures in response to increases in mean arterial pressure (MAP) caused by intravenous infusion of phenylephrine, thus indicating a tonic facilitatory influence action of vMPFC glutamate receptors on the parasympathetic component of the baroreflex. The effect of blockade of vMPFC-NMDA receptors by AP7 was similar to that observed after KYN, suggesting mediation via NMDA receptors. Pretreatment with the NOS inhibitor L-NAME or the specific neural NOS (nNOS) N(omega)-propyl-l-arginine microinjected in the vMPFC caused a shift of the reflex threshold toward higher pressures that was similar to that observed after blockade of NMDA receptors, thus indicating participation of the NO/NMDA-receptor pathway in the vMPFC modulation of the parasympathetic component of the baroreflex. In conclusion, our data indicate that glutamatergic neurotransmission in the vMPFC has a tonic facilitatory influence on the parasympathetic component of the baroreflex. Because local treatment with either the nNOS inhibitor N(omega)-propyl-l-arginine or the specific NMDA antagonist AP7 had similar effects on the baroreflex, it is also suggested that this modulation involves an NMDA-NO interaction within the vMPFC.
Assuntos
Barorreflexo/fisiologia , Óxido Nítrico/fisiologia , Sistema Nervoso Parassimpático/fisiologia , Córtex Pré-Frontal/metabolismo , Receptores de N-Metil-D-Aspartato/fisiologia , 2-Amino-5-fosfonovalerato/análogos & derivados , 2-Amino-5-fosfonovalerato/farmacologia , Animais , Arginina/análogos & derivados , Arginina/farmacologia , Barorreflexo/efeitos dos fármacos , Pressão Sanguínea/efeitos dos fármacos , Vias de Administração de Medicamentos , Inibidores Enzimáticos/farmacologia , Antagonistas de Aminoácidos Excitatórios/administração & dosagem , Frequência Cardíaca/efeitos dos fármacos , Masculino , NG-Nitroarginina Metil Éster/farmacologia , Sistema Nervoso Parassimpático/efeitos dos fármacos , Fenilefrina/administração & dosagem , Córtex Pré-Frontal/efeitos dos fármacos , Ratos , Ratos Wistar , Simpatomiméticos/administração & dosagem , Fatores de Tempo , VigíliaRESUMO
Nitric oxide synthase (NOS) positive neurons are located in most brain areas related to defensive reactions, including the dorsolateral periaqueductal grey (dlPAG). NOS inhibitors injected into this structure induce anxiolytic-like responses whereas NO donors promote flight reactions. Intra-dlPAG administration of carboxy-PTIO, a NO scavenger, or ODQ, a soluble guanylate cyclase inhibitor, produced anxiolytic-like effects on rats exposed to the elevated plus-maze (EPM). A double-staining experiment using NADPHd histochemistry and c-Fos immunohistochemistry in rats exposed to a cat or to the EPM showed increased activation of NO producing neurons in the dlPAG, paraventricular and lateral nuclei of hypothalamus and dorsal raphe nucleus. Cat exposure also increased activation of NOS neurons in the medial amygdala, dorsal pre-mammillary nucleus and bed nucleus of stria terminalis. Local infusion into the dlPAG of a glutamate NMDA-receptor antagonist (AP7) or a benzodiazepine agonist (midazolam) completely prevented the flight reactions induced by intra-dlPAG administration of SIN-1, a NO donor. The responses were also inhibited by the 5-HT2A/C agonist DOI but not by a 5-HT1A agonist. These results suggest a modulatory role for NO on brain areas related to defensive reactions, probably by interacting with glutamate, serotonin and/or GABA-mediated neurotransmission.