Activation of angiotensin II receptors in brain potentiates the stimulating effect of endogenous opioid neurons on central sympathetic outflow.
Endogenous opioid peptides appear to have neurotransmitter or neuromodulator functions in brain mediating a wide variety of effects. We have reported that intracisternal administration of synthetic human beta-endorphin increases plasma concentration of catecholamines, apparently by acting at unknown brain sites to increase sympathetic outflow to the adrenal medulla and sympathetic nerves. In the present study we examined the possibility that angiotensin II, acting in brain, modulates endorphin-induced catecholamine secretion. Simultaneous intracisternal administration of angiotensin II 1.0 nmol together with synthetic human beta-endorphin 1.45 nmol potentiated the plasma epinephrine, norepinephrine and dopamine responses to intracisternal beta-endorphin. In contrast, simultaneous intracisternal administration of the angiotensin II antagonist, [Sar1, Val5, Ala8]-angiotensin II (saralasin), 1.1 nmol together with beta-endorphin, blunted the plasma epinephrine, norepinephrine and dopamine responses to beta-endorphin. These data are consistent with the hypothesis that activation of angiotensin II receptors in brain potentiates the endorphin-induced stimulation of central sympathetic outflow. It remains to be demonstrated whether angiotensin II acting in brain to modulate activity of opioid neurons is synthesized in brain or is derived peripherally.
D000804:Angiotensin II / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002395:Catecholamines / Q000097:blood; D004723:Endorphins / Q000502:physiology*; D008297:Male; D009474:Neurons / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D011945:Receptors, Angiotensin / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D012504:Saralasin / Q000494:pharmacology; D013564:Sympathetic Nervous System / Q000502:physiology*
D002395:Catecholamines; D004723:Endorphins; D011945:Receptors, Angiotensin; D011956:Receptors, Cell Surface; D000804:Angiotensin II; D012504:Saralasin