Vlasova K. Peculiarities of morphofunctional state of the hypothalamus supraoptical nuclei under changed photoperiod conditions

Object - neuron rebuilding of hypothalamic supraoptic nuclei (SON) of rats; objective - to find regularities of changes of neuron morphofunctional condition of the hypothalamic supraoptic nuclei in case of various duration of photoperiod, as well as to detect the role of melatonin in the mechanisms of correction of the detected deviations; methods - morphometric, densitometric, histological, immunohistochemical, electron microscopic, physiological, correlation and regressive analysis, mathematic statistics; results - for the first time more pronounced circadian regularities of the morphofunctional parameter rebuilding of the examined hypothalamic neuroendocrine cells under continuous lighting than in case of light deprivation are found; for the first time on the basis of the conducted ultrastructural examinations of rats under conditions of light stimulation more pronounced destructive disorders in the hypothalamic neurons are found, as well as reduction of their functional activity in the examined periods of the day than in case of light deprivation; on the basis of a comprehensive examination of the character of melatonin receptors density in hypothalamic SON neurons during 24 hours convincing evidence of photo-induced circadian rhythm disorders of melatonin receptors functioning in the examined neuroendocrine cells is received; as a result of the conducted study, for the first time circadian variations of optic density and standard deviation of nuclear staining, nuclear-cytoplasmatic coefficient of pineal gland cells of rats kept under conditions of changed photoperiod are demonstrated; the regularity is proved, according to which introduction of exogenous melatonin (0,5 mg/kg) promotes the increase of ultra-structures resistance to light stimulation, the tendency to normalize cytometric parameters of hypothalamic SON neuron components of rats.