Endogenous opiate peptides, stress reactivity, and risk for hypertension.

Abstract

SUMMARY Endogenous opiate peptides can regulate neuroendocrine and circulatory responses to behavioral stress and may be important in the pathogenic effects of sympathoadrenal reactivity. We tested this hypothesis by examining the effect of the opiate antagonist naloxone on blood pressure responses to behavioral stress in young adults with high, medium, or low casual blood pressures. Naloxone increased mean arterial pressure responses to stress in subjects with low casual pressure, but had no significant effect on responses in subjects with high casual pressure. These results suggest opioidergic inhibition of sympathetic nervous system responses may be deficient in persons at risk for essential hypertension. The mechanism underlying sympathoadrenal hyperreactivity is unknown despite the potential importance of this issue to the etiology of essential hypertension. Opiate peptide systems have a close anatomical relationship to circulatory reflex pathways, and their role in blood pressure regulation has only recently been appreciated. For example, opioid cell bodies or receptors have been found in nucleus tractus solitarius, locus coeruleus, nucleus intermediolateralis, and other nuclei involved in central control of blood pressure. Additionally, these peptides are present in anterior and

Opioids in the systemic hemodynamic and renal responses to stress in spontaneously hypertensive rats.

“…In related studies in conscious rats, naloxone has also been shown to reverse the pressor responses induced by a variety of stressful environmental stimuli such as intense light and sound, cold, foot shock, and brief isolation, 1314 thus supporting a role for opioid peptides in the pressor responses to acute environmental stressors. These results are different from those of McCubbin et al, 33 who showed that during psychological (mental) stress in human subjects naloxone increased mean arterial pressure in persons with low casual mean arterial pressure but had no significant effect on responses in people with high casual mean arterial pressure. These contrasting findings may reflect differences in species or responses that occur from different types of acute stressors (environmental vs. mental).…”

Altered pituitary hormone response to naloxone in hypertension development.

“…10 Recent findings of naloxone antagonism of the hypotensive effects of clonidine suggest altered brainstem opioids in hypertension, 24 -26 and the relation of these mechanisms to baroreceptor reflex and pituitary function has not been determined. Nevertheless, several facts are consistent with altered opioid input to hypothalamic mechanisms mediating risk-group differences, including the anatomic substrate, 22 the effects of naloxone on orthostasis, 10 the behavioral concomitants of opioid antagonism, 9 and the present findings linking anterior pituitary function and blood pressure reactivity. These data, taken together, suggest that naloxone-sensitive opioid pathways inhibit the hypothalamo-pituitarysympathoadrenomedullary cascade, and reduced expression of these opioid mechanisms may have a role in the exaggerated stress reactivity observed in young adults at enhanced risk for essential hypertension.…”

“…6 -8 Recent work with the stereospecific opioid antagonist naloxone suggests diminished opioid inhibition of circulatory responses during stress in young adults with blood pressure dysregulation and enhanced risk for essential hypertension. 9 Pretreatment with naloxone potentiates blood pressure responses during mild psychological stress in persons with low casual blood pressure, but has no pressor effect in persons with high casual blood pressure. This diminished pressor effect of naloxone is not observed during orthostatic challenges, suggesting that the altered opioinhibitory mechanism of blood pressure control in hypertension development occurs in circuitry that is parallel with or rostral to baroreceptor reflex pathways.…”

β-Endorphin in pressor response to hyperventilation in elderly patients with essential and secondary hypertension

“…Different forms of stress activate the endogenous opioid system that, in turn, contributes to changes in systemic cardiovascular function [12][13][14].…”