RESUMO
Neurotransmitter switching in the adult mammalian brain occurs following photoperiod-induced stress, but the mechanism of regulation is unknown. Here, we demonstrate that elevated activity of dopaminergic neurons in the paraventricular nucleus of the hypothalamus (PaVN) in the adult rat is required for the loss of dopamine expression after long-day photoperiod exposure. The transmitter switch occurs exclusively in PaVN dopaminergic neurons that coexpress vesicular glutamate transporter 2 (VGLUT2), is accompanied by a loss of dopamine type 2 receptors (D2Rs) on corticotrophin-releasing factor (CRF) neurons, and can lead to increased release of CRF. Suppressing activity of all PaVN glutamatergic neurons decreases the number of inhibitory PaVN dopaminergic neurons, indicating homeostatic regulation of transmitter expression in the PaVN.
Assuntos
Encéfalo/metabolismo , Dopamina/metabolismo , Neurônios Dopaminérgicos/fisiologia , Luz , Neurotransmissores/metabolismo , Estresse Fisiológico , Animais , Encéfalo/patologia , Encéfalo/efeitos da radiação , Células Cultivadas , Hormônio Liberador da Corticotropina , Neurônios Dopaminérgicos/citologia , Hipotálamo/metabolismo , Hipotálamo/patologia , Hipotálamo/efeitos da radiação , Masculino , Neurotransmissores/efeitos da radiação , Núcleo Hipotalâmico Paraventricular/metabolismo , Núcleo Hipotalâmico Paraventricular/patologia , Núcleo Hipotalâmico Paraventricular/efeitos da radiação , Ratos , Ratos Long-Evans , Receptores Dopaminérgicos/metabolismo , Proteína Vesicular 2 de Transporte de Glutamato/metabolismoRESUMO
The structural changes of neurons of the rat hypothalamic supraoptic (SON) and of paraventricular (PVN) nucleus after 48 h of bright light exposure, of 5 Gy whole-body X-irradiation and of their combination subjected to the analysis by means of light-optic and of electron microscopy for the estimation of radimodificated effect of light exposure lasted 24 h a day and plasticity of neuroendocrine transducers interacted with the optic sensory system. The structural changes of neurons of the SON after combined action are less considerable and more prolonged in comparison with the PVN that loas defermined by their direct connection with the optic sensory system via the retinohypothalamic tract.
Assuntos
Luz , Sistemas Neurossecretores/efeitos dos fármacos , Sistemas Neurossecretores/efeitos da radiação , Raios X , Animais , Hipotálamo/efeitos dos fármacos , Hipotálamo/efeitos da radiação , Hipotálamo/ultraestrutura , Masculino , Microscopia Eletrônica , Sistemas Neurossecretores/ultraestrutura , Núcleo Hipotalâmico Paraventricular/efeitos dos fármacos , Núcleo Hipotalâmico Paraventricular/efeitos da radiação , Núcleo Hipotalâmico Paraventricular/ultraestrutura , Ratos , Irradiação Corporal TotalRESUMO
Utilizing push-pull perfusion, we examined secretary profiles of corticotropin-releasing hormone (CRH) in the nucleus paraventricularis (PVN) of freely moving intact (INT) and ovariectomized (OVX) rats, and in the meanwhile the effects of electroacupuncture (EA) on the release patterns of CRH were observed. The PVN was perfused with artificial cerebrospinal fluid between 08:00 and 12:00 h, and perfusates were collected every 10 min. The average CRH output was significantly larger in OVX rats than that in INT and INT with EA (INT+EA) groups. Interestingly enough, the CRH output showed a significant elevation in OVX with EA (OVX+EA) group during the EA procedure and further increase immediately after the EA. It is the first time to present the temporal profiles of CRH secretion in the PVN of OVX and OVX+EA rats.
Assuntos
Hormônio Liberador da Corticotropina/metabolismo , Eletroacupuntura , Núcleo Hipotalâmico Paraventricular/metabolismo , Análise de Variância , Animais , Feminino , Ovariectomia/métodos , Núcleo Hipotalâmico Paraventricular/efeitos da radiação , Perfusão/métodos , Radioimunoensaio/métodos , Ratos , Ratos Sprague-Dawley , Fatores de TempoRESUMO
Male rat experiments have established that preventive intake of mineral water before exposure to radiation prevents or decreases significantly ultrastructural alterations in paraventricular hypothalamic nucleus.