The partial agonist properties of levocabastine in neurotensin-induced analgesia

The antihistaminic drug levocabastine is a ligand for the low affinity neur otensin receptor (NTS2). Its intracerebroventricular administration to mice induced a significant analgesia in the writhing test but not in the hot pl ate test. In the writhing test, levocabastine decreased neurotensin-induced analgesia to a level not significantly different from the effects of levoc abastine alone. In the hot plate test, levocabastine had no analgesic effec t but completely reversed the neurotensin-induced analgesia. Mepyramine, an other antihistaminic drug, did not share these levocabastine effects. Neith er levocabastine nor mepyramine modified the colonic temperature or reverse d the neurotensin-induced hypothermia. Thus, levocabastine behaves as a par tial agonist at neurotensin NTS2 receptors, which are involved in visceral nociception, but not at yet unidentified neurotensin receptors involved in hypothermia. (C) 1999 Elsevier Science B.V. All rights reserved.