Hypotensive and bradycardic effects of centrally administered vasopressin in stroke-prone spontaneously hypertensive rats.

The cardiovascular effects of centrally administered arginine vasopressin were studied in stroke-prone spontaneously hypertensive rats and Wistar-Kyoto rats. Arginine vasopressin was infused intracerebroventricularly into conscious rats at a rate of 2 pg/kg/min (4.6 microliter/hr) for 21 hours, and blood pressure and heart rate were monitored. Arginine vasopressin caused transient hypertension and tachycardia in Wistar-Kyoto rats, whereas it induced delayed hypotension and bradycardia in stroke-prone spontaneously hypertensive rats. The effects on the latter lasted for 24 to 72 hours after cessation of the infusion. Intravenous administration of arginine vasopressin at a rate of 2 pg/kg/min did not cause any change in blood pressure and heart rate in these rats. These results suggest that arginine vasopressin acts centrally to depress cardiovascular activities, at least in stroke-prone spontaneously hypertensive rats.