Morphine hyperthermia in rats: Role of neurochemical substances in the brain

Abstract

The central neurochemical mechanism underlying the hyperthermic effect of morphine has been investigated in rats. 200 μg morphine hydrochloride, when administered through cerebroventricular route at different seasonal air temperatures caused a rise in rectal temperature of rats. This hyperthermia was not affected by prior administration of antiserotonergic (pCPA, 5,6-DHT) or anticatecholaminergic (PBZ, 6-OHDA) drugs, as well as by PGE synthetase inhibitor, indomethacin. Similarly, cholinergic muscarinic or nicotine receptor blockers, such as atropine and pentolinium/D-tubocurarine, respectively, were ineffective in modifying it. In contrast, the depletion of acetylcholine in brain induced by pretreating the animals with hemicholinium profoundly delayed the hyperthermia, suggesting a central cholinergic involvement in morphine-induced hyperthermia in rats.