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

Abstract

Intracerebral injection of morphine sulfate (0.4 to 4.0 ug) in unanesthetized mice markedly inhibited gastrointestinal propulsive activity. Since a 50-times greater dose is required intravenously for an equivalent effect, this action must be mediated through the central nervous system. Similar responses occur in rats and guinea pigs. Pharmacological inhibition of this morphine action could not be demonstrated with a wide variety of autonomic blocking agents or central nervous system depressants. Concurrent, surgical interruption of sympathetic and parasympathetic outflows from the central nervous system to the gastrointestinal tract also failed to block the activity. Findings suggest morphine may be causing inhibition of gut propulsive action by initiating a neurohumoral discharge from the central nervous system into the blood circulation.