RESUMO
Light and electron microscopic methods were used to analyze changes in secretory neurons in the supraoptic (SON) and paraventricular (PVN) nuclei in the hypothalamus in 100 adult male rats at time points from the first minutes to 180 days after 48 hours of full-time exposure to bright light. At the early time points after exposure, the cellular formulae of the SON and PVN shifted towards functionally active neurons with minimal quantities of secretory granules, large nuclei and nucleoli, low RNA contents, small numbers of rough endoplasmic reticulum cisterns, vacuoles, and lysosomes in the perikarya. The number of cells depositing secretion was greater than in controls at 24 h in the SON and PVN and at 10 days in the SON. Normalization of the cellular formula and the structural organization of the protein-synthesizing apparatus of PVN neurons occurred at 10-30 days, with normalization in the SON at 30-180 days. These data provide evidence that the range of plasticity of neurons in the PVN on exposure to full-time bright light was more significant than that in the SON.
Assuntos
Plasticidade Neuronal/fisiologia , Neurônios/ultraestrutura , Sistemas Neurossecretores/ultraestrutura , Núcleo Hipotalâmico Paraventricular/ultraestrutura , Núcleo Supraóptico/ultraestrutura , Adaptação Fisiológica , Animais , Grânulos Citoplasmáticos/ultraestrutura , Retículo Endoplasmático/ultraestrutura , Complexo de Golgi/ultraestrutura , Luz , Masculino , Plasticidade Neuronal/efeitos da radiação , Neurônios/efeitos da radiação , Sistemas Neurossecretores/fisiologia , Sistemas Neurossecretores/efeitos da radiação , Núcleo Hipotalâmico Paraventricular/metabolismo , Núcleo Hipotalâmico Paraventricular/efeitos da radiação , Fotoperíodo , Ratos , Núcleo Supraóptico/metabolismo , Núcleo Supraóptico/efeitos da radiação , Vasopressinas/metabolismo , Vasopressinas/efeitos da radiaçãoRESUMO
The enzyme activities of cyclic AMP system in the neuro- and adenohypophyses were studied, immediately after an irradiation by a single whole body exposure of 1600 R, in an attempt to find whether this intervention causes the changes in the responsiveness of the cyclic AMP regulatory system. In the irradiated rats the neurohypophyses revealed a reduced activity of adenylate cyclase, moderately increased activity of phosphodiesterase and slightly decreased activity of protein kinase, including the value stimulated by cyclic AMP. In the adenohypophyses the irradiation did not cause any significant changes in the enzyme activities of the cyclic AMP system, except of slightly decreased adenylate cyclase activity. The possible relationship of the plasma level of antidiuretic hormone immediately after irradiation and the enzyme activities of cyclic AMP system is discussed.