Effect of testosterone and its metabolites upon the level of vasopressin messenger ribonucleic acid in the hypothalamus of the hyperosmotically stimulated male rat.

We previously reported that gonadal steroids modify the expression of arginine vasopressin (AVP) in the hypothalamus of rats administered 2% sodium chloride solution for 5 days. Gonadectomy prevented, and testosterone (T) replacement restored, enhanced AVP mRNA levels in the supraoptic nucleus (SON) of male rats receiving this hyperosmotic challenge. The present study investigated the effects of the androgenic and estrogenic metabolites of T on hypothalamic AVP mRNA levels in response to chronic hyperosmolality. Gonadectomized male rats receiving 2% NaCl for 5 days and treated with T, dihydrotestosterone (DHT), or DHT+estradiol (E2), but not E2 alone or empty implants, had increased AVP mRNA levels compared to gonadectomized animals receiving tap water. Our results support a role for T and DHT-mediated effects upon the enhanced accumulation of AVP mRNA in the SON of male rats receiving a chronic hyperosmotic challenge.