RESUMO
Ever since the seminal studies of Hans Selye, activation of hypothalamus-pituitary-adrenal (HPA) axis is emblematic of stress. Consequently, the lack of HPA axis responses following the undisputable psychological stress of a panic attack stands out as one of the most intriguing findings of contemporary psychiatry. On the other hand, the defensive behaviors and aversive emotions produced by stimulation of the dorsal periaqueductal gray matter (DPAG) have been proposed as a model of panic attacks. Therefore, we examined whether the plasma levels of 'stress hormones' corticotropin and prolactin show any change following the DPAG-evoked freezing and flight behaviors of the rat. Rats bearing an electrode into the DPAG and an intra-atrial catheter were stimulated at 9:00 a.m., 18-24 h after the catheter implantation. Blood samples were withdrawn just before 1-min stimulation of DPAG, immediately after (5 or 15 min) and throughout 3 to 27 h following stimulation. In another experiment, samples were withdrawn either before or following a prolonged stimulation (5 min) of the DPAG with flight threshold intensity. Hormones were measured by either chemiluminescent or double-antibody immunoassays. Hormone plasma levels following freezing and flight behaviors were compared to those of resting or restraint-stressed rats. Data show that stress hormones remain unaltered following the DPAG-evoked defensive behaviors. Not even the 5-min stimulation of DPAG with the flight threshold intensity changed corticotropin plasma levels significantly. As far as we known, this is the first demonstration of the lack of stress hormone responses following the intense emotional arousal and physical exertion of a fear-like behavior in rats. Data add new evidence of DPAG involvement in spontaneous panic attacks.
Assuntos
Adaptação Psicológica/fisiologia , Transtorno de Pânico/etiologia , Estresse Fisiológico/fisiologia , Hormônio Adrenocorticotrópico/sangue , Animais , Mapeamento Encefálico , Estimulação Elétrica , Reação de Fuga/efeitos dos fármacos , Reação de Fuga/fisiologia , Reação de Congelamento Cataléptica/efeitos dos fármacos , Reação de Congelamento Cataléptica/fisiologia , Masculino , Modelos Biológicos , Monossacarídeos de Poli-Isoprenil Fosfato/farmacologia , Prolactina/sangue , Ratos , Ratos Wistar , Estimulação QuímicaRESUMO
Blood pressure changes were evoked in the anaesthetized rabbit and rat by stimulating electrically within the caudal raphe nuclei. The responses evoked in the two species were very different, mainly pressor in the rat (85% pressor, 5% depressor) compared with approximately similar proportions of depressor and pressor in the rabbit (29% and 27%, respectively). The responses evoked from a particular site could not be reversed by changing the stimulus strength. It is proposed that the haemodynamic responses evoked in the rabbit and the rat, in response to stimulation within raphe, are related to differences in the central organization of these nuclei and/or their connexions. These results are then discussed in relation to the observation that the tonic phase of desynchronized sleep is accompanied by hypotension in the rabbit and hypertension in the rat. Finally, it is suggested that the haemodynamic differences observed during desynchronized sleep in these two species are caused by differences in central nervous regulation which involve the caudal raphe nuclei, magnus, pallidus and obscurus (AU)
Assuntos
Coelhos , Ratos , Animais , Estudo Comparativo , Núcleos da Rafe , Estimulação Elétrica , Pressão Sanguínea , SonoRESUMO
Blood pressure changes were evoked in the anaesthetized rabbit and rat by stimulating electrically within the caudal raphe nuclei. The responses evoked in the two species were very different, mainly pressor in the rat (85% pressor, 5% depressor) compared with approximately similar proportions of depressor and pressor in the rabbit (29% and 27%, respectively). The responses evoked from a particular site could not be reversed by changing the stimulus strength. It is proposed that the haemodynamic responses evoked in the rabbit and the rat, in response to stimulation within raphe, are related to differences in the central organization of these nuclei and/or their connexions. These results are then discussed in relation to the observation that the tonic phase of desynchronized sleep is accompanied by hypotension in the rabbit and hypertension in the rat. Finally, it is suggested that the haemodynamic differences observed during desynchronized sleep in these two species are caused by differences in central nervous regulation which involve the caudal raphe nuclei, magnus, pallidus and obscurus