Vasopressin and oxytocin content are decreased in the brain stems of spontaneously hypertensive rats.

The brain stem and neurohypophyseal content of arginine vasopressin and the brain stem content of oxytocin were measured by radioimmunoassay in 3-, 7-, and 22- to 28-week-old spontaneously hypertensive rats of the stroke-prone strain (SHRSP) and the values were compared to those measured in age-matched normotensive Wistar-Kyoto rats (WKY). When compared to WKY, the content of vasopressin in the brain stems of SHRSP was reduced in all three age-groups; in contrast, the neurohypophyseal contents of vasopressin in the two species were not significantly different at 3 and 7 weeks of age and the content was increased slightly in SHRSP at 22-28 weeks. Similar to the findings for vasopressin in the brain stem, the content of oxytocin in this tissue was reduced in SHRSP at 7 and 22-28 weeks of age. The results demonstrate that brain stem arginine vasopressin levels and neurohypophyseal arginine vasopressin levels may change differentially and that the age-related differences in the brain stem levels of arginine vasopressin and oxytocin in SHRSP and WKY are consistent with the possibility that these peptides may play a role in altering cardiovascular reflex activity.