Hypertension research : official journal of the Japanese Society of Hypertension
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It has been demonstrated that opioids modulate the renin-angiotensin and sympathetic nervous system. To clarify the interaction of central angiotensin II (Ang II) and endogenous opioids, we studied the effects of naloxone, an opioid antagonist, on cardiovascular and sympathetic responses to intracerebroventricular (i.c.v.) Ang II in conscious rabbits. I.c.v. ⋯ Ang II (8.9 +/- 2.2 vs. 16.2 +/- 0.7%, p < 0.05). Combined pretreatment with naloxone and V1-receptor antagonist further increased MAP and RSNA in response to ICV Ang II (20 +/- 1 vs. 16 +/- 2 mmHg, p < 0.05, and 30.9 +/- 3.7 vs. 16.2 +/- 0.7%, p < 0.01, respectively). These results suggest that opioids and AVP synergistically modulate sympathetic outflow so as to suppress the central pressor action of Ang II in conscious rabbits.