The vasopressinergic innervation of the brain in normal and castrated rats

TLDR

The study maps vasopressin‑immunoreactive structures in intact adult male rat brains, noting that hypothalamic pathways remain unchanged after castration. The authors used a modified immunocytochemical technique to identify vasopressin‑immunoreactive fibers in previously unreported brain regions. Castration eliminated vasopressin cell bodies in the bed nucleus of the stria terminalis and medial amygdaloid nucleus and markedly reduced fiber density in numerous limbic and midbrain regions, effects that were prevented by testosterone and indicate that gonadal hormones are essential for the normal development of these projections, whereas hypothalamic vasopressin pathways remain unaffected.

Abstract

A detailed description is given of the distribution of vasopressin-immunoreactive structures in the brain of intact adult male rats. By application of a modified immunocytochemical procedure, vasopressin-immunoreactive fibers were detected in many new areas. In adult male rats which were castrated 15 weeks before death, vasopressin-immunoreactive cell bodies had disappeared from the bed nucleus of the stria terminalis and the medial amygdaloid nucleus. No obvious changes were found in vasopressin-immunoreactive cell bodies in other areas. Furthermore, a very strong reduction was seen in the density of vasopressin-immunoreactive fibers in the olfactory tubercle, nucleus of the diagonal band and its immediate surroundings, ventral pallidum, basal nucleus of Meynert, lateral septum, septofimbrial nucleus, ventral hippocampal formation, amygdaloid area, pre- and supramammillary nucleus, supramammillary decussation, (inter)dorsomedial, parafascicular, and ventral aspect of paraventricular thalamic nuclei, zona incerta, lateral habenular nucleus, ventral tegmental area, substantia nigra, periventricular gray, dorsal and median raphe nucleus, and locus coeruleus. No changes were observed in other areas containing vasopressin-immunoreactive fibers. These changes following gonadectomy were not observed in castrated rats which had been treated with testosterone. The results suggest that vasopressin projections from the bed nucleus of the stria terminalis and possibly from the medial amygdaloid nucleus require the presence of gonadal hormones for their normal appearance. This is in contrast to pathways arising from the hypothalamic vasopressin-producing nuclei, which fail to show obvious changes following castration.