Influence of chronic naloxone treatment on development of hypertension in the spontaneously hypertensive rat.

Chronic administration of naloxone by means of miniosmotic pumps retarded the development of hypertension in young spontaneously hypertensive rats (SHRs) in a dose-related manner. Abrupt termination of naloxone treatment resulted in acceleration in the rate of the blood pressure increase, while increasing the naloxone concentration further slowed the development of hypertension in SHRs. The heart rates of SHRs undergoing chronic naloxone treatment were generally lower than those of control SHRs. Naloxone had no influence upon the mean systolic blood pressures or heart rates of normotensive Wistar-Kyoto control rats. These findings indicate that chronic naloxone treatment can alter the development of hypertension in the SHR.