Intrahypothalamic injection of deltorphin-II alters body temperature in rats

The present study investigated the effect of H-Try-D-Ala-Phe-Glu-Val-GIy-NH2 deltorphin-II, a selective delta-2 agonist, and [D-Pen(2), D-Pen(5)]enkephalin, a selective delta-1 agonist, on body temperature in the rat. Microinjected into the preoptic anterior hypothalamus (POAH), deltorphin-II (0.1-1 mug) produced an immediate dose-related hyperthermia following injection. Injection of the delta-2 antagonist naltriben into the preoptic anterior hypothalamus (1 mug, 30 min prior to deltorphin-II) significantly attenuated the deltorphin-II-induced hyperthermia. Microinjection of [D-Pen(2) D-Pen-(5)]enkephalin into the POAH (0.1-3 mug) did not affect Tb. The data demonstrate that delta-2 receptors are involved in the mediation of Tb effects, and deltorphin-II exerts its action directly on thermosensitive cells of the preoptic anterior hypothalamus. Delta-1 opioid receptors do not appear to be involved in the control of body temperature. (C) 2004 Published by Elsevier B.V.