RELATIONSHIP BETWEEN CHRONIC EXPOSURE TO STRESS AND DEVELOPMENT OF HYPERTENSION

The relationship between stress and hypertension has long been a topic of debate. Until recently, no animal (nor physical) model existed whi ch incorporated these two parameters together, hence accurate assessme nts of their interactions were postulations, at best. The borderline h ypertensive rat (BHR) is an animal model in which arterial hypertensio n will ensue only when the rat is subjected to a chronic stressor. The refore, this animal model offers an opportunity to study the physiolog ical consequences of a given stressor on the entire organism during th e course of the development of hypertension. The cardiovascular and hu moral effects of chronic exposure to a physiological stressor on the B HR, at rest and during exposure to an acute and novel stress, have bee n examined and are presented in this paper. The involvement of the cen tral nervous system in the regulation of this stress induced hypertens ive state has been hypothesized to play a major role in the regulation of the stress and hypertensive relationship. Of particular importance are the endogenous opioids and their influence on the maintenance of homeostasis during periods of physiological stress. The localization o f the endogenous opioid enkephalin in the paraventricular nucleus of t he hypothalamus (PVN), an important brain region in the regulation of the stress response further substantiates the involvement of the opioi d system during stress induced hypertension. Immunohistochemical data on the localization of ENKergic fibers in the PVN and other brain regi ons are similarly discussed in this paper.