Gonadal hormone actions on the morphology of the vasopressinergic innervation of the adult rat brain.

Castration of adult male rats resulted in a gradual decrease in vasopressin fiber density over a period of 15 weeks to a point where hardly any fibers were found in those areas where the fibers probably are derived from the bed nucleus of the stria terminalis. The original fiber density could be restored by testosterone replacement therapy within 5 weeks. No effects of hormonal manipulations were found in the vasopressin projections of the paraventricular and the suprachiasmatic nucleus. Ovariectomy of female rats resulted in the same changes in the vasopressin fiber pathways, as did castration in males.