Intracerebroventricular injection of senktide-induced Fos expression in vasopressin-containing hypothalamic neurons in the rat

Intracerebroventricular injection of senktide, a selective agonist for neur okinin B receptor (NK3), induced Fos expression in many neurons of the rat hypothalamus. Fos-positive neurons were predominantly present in the suprao ptic and paraventricular hypothalamic nuclei, and some of them were seen in the lateral preoptic area, lateral hypothalamic area, arcuate nucleus, per ifornical region, posterior hypothalamic area, circular nucleus, and along relatively large blood vessels (lateral hypothalamic perivascular nucleus) in the anterior hypothalamus. A double labeling study was performed to exam ine if vasopressin-containing neurons in the hypothalamus could be activate d by the treatment. Neurons with both Fos-like immunoreactivity (-LI) and v asopressin-LI were found in the paraventricular nucleus, supraoptic nucleus , circular nucleus and lateral hypothalamic perivascular nucleus. In the su praoptic nucleus, about 87% of vasopressin-containing neurons exhibited Fos -LI, which corresponded to about 64% of Fos-positive neurons in the nucleus . In the paraventricular nucleus, about 80% of vasopressin-like immunoreact ive neurons exhibited Fos-LI, which constituted about 51% of the total popu lation of Fos-positive neurons in the region. The results suggest that NK3 receptor may be involved in the modulation of release of vasopressin from t he hypothalamus in the rat. (C) 2000 Elsevier Science B.V. All rights reser ved.