[Effect of continuous illumination and disruption of monoaminergic innervation on the hypothalamus of the female rat].

Hypothalamic suprachiasmatic nucleus (Schn) and Arquate nucleus (AN) were studied in female rats kept under constant illumination (rats with persistent estrus) or under light-dark cyclic illumination (normal estrus cycle). To destroy monoaminergic terminals, some rats from each group were injected with neurotoxic agents into the lateral cerebral ventricle. 6-hydroxydophamine which disturbs catecholaminergic terminals induced activation of the Schn and AN in rats with persistent estrus only. Destruction of serotoninergic terminals with 5,6-hydroxytryptophan induced activation of the Schn in rats with normal sex cycle and in those with a persistent estrus; the AN was also activated but only in rats with normal estrous cycle. As reported earlier, destruction of serotoninergic terminals withstands the decrease of plasma LH under constant illumination although persistent estrus still lasts. It seems there are different parallel ways to disturb normal sex cycle under constant light illumination.