SOCIAL DEPRIVATION STRESS INDUCES ADAPTATIVE CHANGES OF OPIOID MECHANISMS IN THE RAT TAIL ARTERY

Brief (7-14 days) social deprivation stress has been found to increase blood pressure in Wistar rats, an effect dependent on activation of o pioid function. The role of central opioids in this and other response s to stress has been repeatedly determined, but the possible involveme nt of modifications of peripheral opioid mechanisms is poorly understo od. To further increase this knowledge, we have examined the opioid se nsitivity of tail arteries taken from social deprived Wistar rats by s tudying the effect of beta-endorphin and DADLE ''in vitro''. Both opio ids inhibited the electrically-induced constriction of the preparation s in a dose-dependent manner, but these actions were significantly att enuated after 7-14 days of social deprivation. When the rats were isol ated for 30-35 days, the hypertensive response was still present but t he arteries from group-housed and isolated animals no longer showed di fferential sensitivity to opioids; This difference with respect to 7-1 4 days of isolation could be related to age-dependent changes of opioi d function, which were observed among group-housed animals. The result s suggest that social deprivation stress induces an adaptation of the tail arteries to the opioid effects on contractility. It is suggested that this endogenous adaptation could be contributing to the hypertens ive response observed after social deprivation.