Centrally Mediated Inhibition of Gastrointestinal Propulsive Motility By Morphine over a Non-Neural Pathway

Abstract

Summary

1. Intracerebral injection of small amounts (0.4 to 4.0 μg) of morphine sulfate in unanesthetized mice causes marked inhibition of gastrointestinal propulsive activity. Since a 50-times greater dose is required intravenously for an equivalent effect, this action of morphine upon the gut must be mediated through the central nervous system. Similar actions have also been observed in rats and guinea pigs. 2. Pharmacological inhibition or blockade of this morphine action upon the gut could not be demonstrated with a wide variety of autonomic blocking agents or central nervous system depressants. Concurrent, surgical interruption of the sympathetic and parasympathetic outflows from the central nervous system to the gastrointestinal tract also failed to block the activity. 3. The findings suggest that morphine may be causing inhibition of gut propulsive action by initiating a neurohumoral discharge from the central nervous system into all the circulating blood of the body.