Effects of morphine, buprenorphine, pentazocine and nalorphine on acquisition and extinction of active avoidance responses in rats.

The effects of subcutaneous administration of morphine, buprenorphine, pentazocine and nalorphine were studied at two dose levels in rats (low dose x 10 and high dose x 20 of equivalent human dose) on the performance of active avoidance responses using a shuttle box. Pretraining injections of both doses of pentazocine and low dose nalorphine impaired acquisition on day 1 and day 2. Morphine and buprenorphine (at both dose levels) and high dose nalorphine did not affect the acquisition process. Post-training administration of morphine (high dose) and buprenorphine (both doses) delayed extinction of active avoidance responses. Low dose of morphine, high dose of pentazocine and both doses of nalorphine did not appreciably affect the extinction process. Mu opioid receptor agonists probably act as reinforcers to facilitate memory.

On the Effect of Morphine Hydrochloride on the Mesenteric Mast cells of Albino Rats

Histological studies were carried out on the degranulation of mesenteric mast cells of white rats caused by injections of morphine and nalorphine hydrochloride intravenously and the following conclusions were obtained. 1. By the injection of morphine hydrochloride fairly significant degranulation of the mesenteric mast cell was observed. 2. In various experimental doses of morphine hydrochloride the cytological change of the degranulation was not proportional to the doses of it in cases given more than 12mg./kg. of body weight. 3. The degranulating effect of the mesenteric mast cell by the injection of morphine hydrochloride was significantly inhibited by an adrenalectomy.