Vasopressin- and oxytocin-immunoreactive nerve cells in the aging rat hypothalamus.

Immunohistochemistry and morphometry were used to study the age-related changes in the vasopressin (AVP) and oxytocin (OXT) nerve cells in the paraventricular (PVN), supraoptic (SON) and suprachiasmatic (SCN) nuclei of 3-, 11- and 28-month-old rats. The results showed a statistically significant reduction in the mean number of AVP cells in the PVN, SON and SCN, and of OXT cells in the PVN with advancing age. Different age-related changes in the mean size of the immunoreactive cells were found in the three nuclei: a significant and transitory increase in the AVP and OXT cell sizes in the PVN, a tendency towards increasing the AVP and OXT cell sizes in the SON, and a significant and gradual decrease in the AVP cell size in the SCN. The combination of the morphometric data and staining patterns of the AVP and OXT perikarya and fibers in the PVN and SON pointed to an increased transport of AVP and OXT in 11-month-old rats as well as to a decreased production of these peptides in the PVN of 28-month-old rats. Taken together the staining pattern and the morphometric results showed a progressive loss of AVP cells in the SCN in aging.