Stereoselectivity and subtype of the opiate receptor involved in stress-induced hypertension

Abstract

Naloxone enantiomorphs were given intracerebroventricularly (i.c.v.) to rats socially deprived for a brief period of time (7–14 days) in order to ascertain the mediation of central opiate receptors in the reversal effect of opiate antagonists on the high systolic blood pressure induced by this type of stress. While the active enantiomorph ((−)-naloxone, 20 nmol per rat) lowered the elevated blood pressure, the (+)-enantiomorph (which shows a 10 000-fold lower affinity for opiate receptors) had no effect. Additionally, the antihypertensive effect induced by i.c.v. administration of an antagonist of the μ-opiate receptor (β-funaltrexamine, 20 nmol per rat), but not of the δ-opiate receptor (ICI 174, 864, 15 nmol per rat) pointed to the involvement of μ-opiate receptors as the endogenous component of the hypertensive response of rats to stress.