Effect of Morphine and Its Conjugates on the Isolated Ileal Preparation of Guinea-pig

Abstract

The present study was undertaken to reconfirm the previous conclusion that morphine-6-conjugates cause potent analgesia by themselves in mice. For this purpose, inhibitory effect of morphine and its three pairs of 3- and 6-conjugates (glucuronides, ethereal sulfates and phosphates) to nicotine-induced contraction of the isolated guinea-pig ileum was examined. The potency of these conjugates was found to decrease in the following order, morphine-6-sulfate> morphine-6-glucuronide> morphine, morphine-3- and 6-phosphate> morphine-3-glucuronide, morphine-3-sulfate, indicating fairly good accordance with order in their analgesic effects in mice. The present experiment again provided strong suggestion that the above biological effect was attributable to the conjugates themselves. © 1977, The Pharmaceutical Society of Japan. All rights reserved.