INTERACTIONS BETWEEN ANGIOTENSIN-II AND DELTA-OPIOID RECEPTOR SUBTYPEAGONISTS UPON WATER-INTAKE IN RATS

Delta opioid receptor agonists, like those of mu and kappa receptors, stimulate water intake. To assess the relative contributions of delta( 1) and delta(2) receptors in the modulation of water intake stimulated by Angiotensin II (AII), the present study examined the respective ac tions of [D-Pen(2), D-Pen(5)]-enkephalin (DPDPE: 5-20 ug, icv) and [D- Ala(2), Glu(4)]-Deltorphin (Delt II: 5-20 ug, icv) upon water intake p er se, and upon AII (0.02-20 ng, icv)-induced hyperdipsia in rats. Bot h DPDPE and Delt II dose-dependently stimulated spontaneous water inta ke. An ineffective (5 ug) dose of DPDPE differentially altered water i ntake when paired with AII, significantly increasing intake at the 0.0 2 ng dose, not changing intake at the 0.2 ng dose and significantly de creasing intake at the 2 ng dose. In contrast, pairing ineffective dos es of Delt II (5 ug) and AII (0.2 ng) significantly increased water in take that persisted when either the Delt II dose (1 ug) or the AII dos e (0.02 ng) was lowered. However, neither delta(1) nor delta(2) opioid agonists significantly altered the ED50 for AII-induced drinking. Thu s, delta(2) opioid agonism appeared more consistent and reliable than delta(1) opioid agonism in stimulating water intake when paired with A II, and these data indicate interactions between delta(1) and delta(2) agonists and AII in mediating water intake. (C) 1997 Elsevier Science Inc.