[Electron microscopic characteristics of the neuroendocrine neurons of the amygdaloid body of the brain in male and female rats at different stages of estrous cycle].

Ultrastructural characteristics of neuroendocrine neurons were studied in amygdala dorsomedial nucleus (DMN), which is one of main zones of sexual dimorphism, in 12 Wistar rats with the body mass of 250-300 g, 3 males and 9 females at different stages of the estrous cycle. In each animal, an average of 50 DMN neurons were examined and their functional state was analyzed on the basis of their ultrastructural characteristics. Morpho-functional classification is proposed, that reflects hormone-dependent variations in neuronal activity. It was established that DMN neurons could be found in different structural and functional states, that may be classified as the state of rest, moderate activity, increased activity, stress (peak activity), decrease in activity (two types), return to an initial state and apoptosis. At the stage of estrus, the neurons in the state of increased activity (40% of the total population) and peak activity (26%) were found to prevail. In metestrus, most of the neurons were in the state of type I decrease in activity (with an increase in nuclear heterochromatin content--30% of the cells); peak activity and increased activity were found in 25% and 20% of neurons, respectively. In diestrus, the neurons in the state of rest, moderate and increased activity, peak activity and type I decrease in activity were represented in approximately equal proportions (18%, 21%, 18%, 20% and 16%, respectively). In males, 35% and 22% of neurons, respectively, were found in the state of increased activity and peak activity. Neuronal death was detected only in males.