RESUMO

BACKGROUND: Stimulation of serotonergic neurons within the dorsal raphe dorsomedial subnucleus facilitates inhibitory avoidance acquisition in the elevated T-maze. It has been hypothesized that such anxiogenic effect is due to serotonin release in the basolateral nucleus of the amygdala, where facilitation of serotonin 2C receptor-mediated neurotransmission increases anxiety. Besides the dorsal raphe dorsomedial subnucleus, the dorsal raphe caudal subnucleus is recruited by anxiogenic stimulus/situations. However, the behavioral consequences of pharmacological manipulation of this subnucleus are still unknown. AIMS: Investigate whether blockade of serotonin 2C receptors in the basolateral nucleus of the amygdala counteracts the anxiogenic effect caused by the stimulation of dorsal raphe dorsomedial subnucleus serotonergic neurons. Evaluate the effects caused by the excitatory amino acid kainic acid or serotonin 1A receptor-modulating drugs in the dorsal raphe caudal subnucleus. METHODS: Male Wistar rats were tested in the elevated T-maze and light-dark transition tests after intra-basolateral nucleus of the amygdala injection of the serotonin 2C receptor antagonist SB-242084 (6-chloro-2,3-dihydro-5-methyl-N-[6-[(2-methyl-3-pyridinyl)oxy]-3-pyridinyl]-1H-indole-1-carboxyamide dihydrochloride) followed by intra-dorsal raphe dorsomedial subnucleus administration of the serotonin 1A receptor antagonist WAY-100635 (N-[2-[4-2-methoxyphenyl)-1-piperazinyl]ethyl]-N-2-pyridinil-cyclohexanecarboxamide maleate). In the dorsal raphe caudal subnucleus, animals were injected with kainic acid, WAY-100635 or the serotonin 1A receptor agonist 8-OH-DPAT ((±)-8-hydroxy-2-(di-n-propylamino) tetralin hydrobromide) and tested in the elevated T-maze. RESULTS: SB-242084 in the basolateral nucleus of the amygdala blocked the anxiogenic effect caused by the injection of WAY-100635 in the dorsal raphe dorsomedial subnucleus. Kainic acid in the dorsal raphe caudal subnucleus increased anxiety, but also impaired escape expression in the elevated T-maze. Neither WAY-100635 nor 8-OH-DPAT in the dorsal raphe caudal subnucleus affected rat's behavior in the elevated T-maze. CONCLUSION: Serotonin 2C receptors in the basolateral nucleus of the amygdala mediate the anxiogenic effect caused by the stimulation of serotonergic neurons in the dorsal raphe dorsomedial subnucleus. The dorsal raphe caudal subnucleus regulates anxiety- and panic-like behaviors, presumably by a serotonin 1A receptor-independent mechanism.

Assuntos

Ansiedade/induzido quimicamente , Complexo Nuclear Basolateral da Amígdala/efeitos dos fármacos , Núcleo Dorsal da Rafe/efeitos dos fármacos , Receptor 5-HT2C de Serotonina/efeitos dos fármacos , Serotonina/metabolismo , 8-Hidroxi-2-(di-n-propilamino)tetralina/farmacologia , Aminopiridinas/farmacologia , Animais , Ansiedade/psicologia , Estimulação Elétrica , Indóis/farmacologia , Ácido Caínico , Masculino , Piperazinas/farmacologia , Piridinas/farmacologia , Ratos , Ratos Wistar , Neurônios Serotoninérgicos/efeitos dos fármacos , Antagonistas da Serotonina/farmacologia , Agonistas do Receptor de Serotonina/farmacologia

RESUMO

BACKGROUND: The dorsal hippocampus has a central role in modulating cardiovascular responses and behavioral adaptation to stress. The dorsal hippocampus also plays a key role in stress-associated mental disorders. The endocannabinoid system is widely expressed in the dorsal hippocampus and modulates defensive behaviors under stressful conditions. The endocannabinoid anandamide activates cannabinoid type 1 receptors and is metabolized by the fatty acid amide hydrolase enzyme. AIMS: We sought to verify whether cannabinoid type 1 receptors modulate stress-induced cardiovascular changes, and if pharmacological fatty acid amide hydrolase inhibition in the dorsal hippocampus would prevent the cardiovascular responses and the delayed anxiogenic-like behavior evoked by restraint stress in rats via cannabinoid type 1 receptors. METHODS: Independent groups received intra-dorsal-hippocampal injections of N-(piperidin-1yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-hpyrazole-3-carboxamide (AM251; cannabinoid type 1 receptor antagonist/inverse agonist, 10-300 pmol) and/or cyclohexyl carbamic acid 3'-carbamoyl-biphenyl-3-yl ester (URB597; fatty acid amide hydrolase inhibitor, 10 pmol) before the restraint stress session. Cardiovascular response during restraint stress or later behavioral parameters were evaluated. RESULTS: Acute restraint stress altered the cardiovascular response, characterized by increased heart rate and mean arterial pressure, as well as decreased tail cutaneous temperature. It also induced a delayed anxiogenic-like effect, evidenced by reduced open arm exploration in the elevated plus maze 24 h after stress. AM251 exacerbated the stress-induced cardiovascular responses after injection into the dorsal hippocampus. In contrast, local injection of URB597 prevented the cardiovascular response and the delayed (24 h) behavioral consequences of restraint stress, effects attenuated by pretreatment with AM251. CONCLUSION: Our data corroborate previous results indicating that the hippocampal endocannabinoid system modulates the outcome of stress exposure and suggest that this could involve modulation of the cardiovascular response during stress exposure.

Assuntos

Ansiedade , Pressão Arterial/fisiologia , Comportamento Animal/fisiologia , Agonistas de Receptores de Canabinoides/farmacologia , Antagonistas de Receptores de Canabinoides/farmacologia , Endocanabinoides/fisiologia , Frequência Cardíaca/fisiologia , Hipocampo/metabolismo , Receptor CB1 de Canabinoide/fisiologia , Estresse Psicológico , Amidoidrolases/farmacologia , Animais , Ansiedade/induzido quimicamente , Ansiedade/etiologia , Ansiedade/metabolismo , Ácidos Araquidônicos/farmacologia , Pressão Arterial/efeitos dos fármacos , Comportamento Animal/efeitos dos fármacos , Benzamidas/farmacologia , Agonistas de Receptores de Canabinoides/administração & dosagem , Antagonistas de Receptores de Canabinoides/administração & dosagem , Carbamatos/farmacologia , Modelos Animais de Doenças , Endocanabinoides/farmacologia , Frequência Cardíaca/efeitos dos fármacos , Hipocampo/efeitos dos fármacos , Masculino , Piperidinas/farmacologia , Alcamidas Poli-Insaturadas/farmacologia , Pirazóis/farmacologia , Ratos , Ratos Wistar , Receptor CB1 de Canabinoide/agonistas , Receptor CB1 de Canabinoide/antagonistas & inibidores , Restrição Física/efeitos adversos , Temperatura Cutânea/efeitos dos fármacos , Temperatura Cutânea/fisiologia , Estresse Psicológico/complicações , Estresse Psicológico/metabolismo , Estresse Psicológico/fisiopatologia

RESUMO

The bed nucleus of the stria terminalis (BNST) is a heterogeneous and complex limbic forebrain structure, which plays an important role in controlling autonomic, neuroendocrine and behavioral responses. The BNST is thought to serve as a key relay connecting limbic forebrain structures to hypothalamic and brainstem regions associated with autonomic and neuroendocrine functions. Its control of physiological and behavioral activity is mediated by local action of numerous neurotransmitters. In the present review we discuss the role of the BNST in control of both autonomic and neuroendocrine function. A description of BNST control of cardiovascular and hypothalamus-pituitary-adrenal axisactivity at rest and during physiological challenges (stress and physical exercise) is presented. Moreover, evidence for modulation of hypothalamic magnocellular neurons activity is also discussed. We attempt to focus on the discussion of BNST neurochemical mechanisms. Therefore, the source and targets of neurochemical inputs to BNST subregions and their role in control of autonomic and neuroendocrine function is discussed in details.