[Status of neurocytes of the arcuate and suprachiasmatic nuclei of the hypothalamus and median eminence in rats exposed to prolonged internal irradiation].

Ultrastructural changes caused by single administration of 75Se-selenomethionine (1.22 X 10(4) Bk/g bw) were studied in neurocytes of the arcuate and suprachiasmatic nuclei of the hypothalamus and medial eminence in random-bred male rats. Within the first three months after administration of the radioactive agent, there was an activation of the synthesis of neurocyte secretion granules and release of their content from nerve terminals into the channel of medial eminence portal capillaries. Afterwards (over 6-12 months) the synthesis of of neurocyte secretion material and the release into medial eminence portal capillaries were suppressed. By the 18th month after 75Se-selenomethionine administration there occurred a relative normalization of the structure and function of neurocytes, and activation of the release of the contents of secretion granules from nerve terminals into the channel of medial eminence portal capillaries.