[Role of vasopressin- and oxytocinergic cells of macrocellular rat hypothalamic nuclei in regulating the thyroid during the administration of thyroliberin].

The supraoptic and paraventricular nuclei of the rat hypothalamus were investigated after single (i. p. 1.6 Mg) or repeated (i. p. 0.8 Mg twice a day for 8 days) injections of thyroliberin. Vasopressin- and oxytocinergic cells of these nuclei were identified by immunohistochemical methods. Their response was estimated by changes in the size of cell nucleoli. The plasma concentration of TSH, T3 and T4 was determined by RIA. In the supraoptic nucleus, function of vasopressin- and oxytocinergic cells was depressed throughout the experiment irrespective of the plasma changes of TSH and thyroid hormones. In the paraventricular nucleus, vasopressinergic cells remained unchanged, whereas the changes of oxytocinergic cells followed the pattern opposite to that of plasma TSH. It was assumed that oxytocinergic cells of the paraventricular nucleus were responsible for the blood TSH dynamics and could be involved in the regulation of thyrotropic function. The cause underlying different reactions of cells, being of the same type but localized in the supraoptic or paraventricular nucleus was discussed.