Reserpine ulcers in morphine dependent and withdrawal rats.

Reserpine ulcers were produced in dependent and withdrawal rats. The reactivity of isolated duodenum and colon to morphine and papaverine was tested in both groups of animals. Chronic administration of morphine decreases the development of post reserpine gastric ulcers, while in withdrawal rats it increases their occurrence. Relaxation and contraction responses of duodenum taken from the dependent rats showed tolerance. On the other hand, withdrawal rats displayed increased responses as compared with placebo group. Colon of dependent rats showed stronger responses to morphine and papaverine which indicates the lack of tolerance to morphine or enhanced receptors sensitivity. Stronger responses of colon in both dependent and withdrawal rats suggest the lack of tolerance in this segment of the gut. In withdrawal rats which obtained reserpine and placebo responses to papaverine were similar. It is suggested that reserpine decreased the sensitivity of mu receptor to morphine.