ANP presence in the hypothalamic suprachiasmatic nucleus of developing rat.

In previous research, we studied both the oxytocin and vasopressin ontogeny in the hypothalamic supraoptic and paraventricular nuclei, and the ANP-ontogeny in the hypothalamic supraoptic nucleus. In this paper we evaluate the ANP-ontogeny in the rat hypothalamic suprachiasmatic nucleus; infact the suprachiasmatic nucleus it is known to synthesize vasopressin, a peptidic hormone involved in the homeostasis of the body fluids by an antagonistic role to ANP. Immunohistochemical techniques show that ANP is present in the hypothalamic suprachiasmatic nucleus of the rat at 18 degrees day of i.u. life and at 0 degrees to 3 degrees day of postnatal life. PCR analysis confirms the ANP-mRNA expression. Thus, it is possible to adfirm that the suprachiasmatic nucleus is a synthesis site of ANP, and ANP appears in both the supraoptic and suprachiasmatic nuclei at the same developmental stage. Moreover, ANP and vasopressin appear at the same developmental stage since both the peptides are involved in the homeostasis of body fluids.