FLUNARIZINE ANALGESIA IS MEDIATED BY MU-OPIOID RECEPTORS

We evaluated the opioid antinociceptive mechanism of the calcium chann el blocker flunarizine. Flunarizine produced a dose-dependent, analges ia in the hot plate test which was antagonized by general (naloxone) a nd mu [beta-fualtrexamine (beta-FNA)]-opioid antagonists, indicating a role for CL receptors in flunarizine analgesia. Naltrindole (delta(1) antagonist) did not affect flunarizine analgesia. A fixed subthreshol d dose of flunarizine augmented mu (morphine) analgesia and blocked de lta(1) [enkephalin, [D-Pen(2,5)] (DPDPE)] analgesia. Apparently, fluna rizine has mu agonistic activity and delta(1) antagonist or mixed agon istic-antagonistic activity. (C) 1997 Elsevier Science Inc.