Abstract
Summary
Intracerebral injection of small amounts (3.5—60 μg/rat) of morphine sulfate in intact rats caused a marked suppression of gastrointestinal propulsive activity. Since 11 times greater amounts of morphine are required intravenously for an equivalent effect, the constipating action of morphine upon the gut primarily occurs via the central nervous system. The intracerebral injection of similarly small amounts of morphine into the donor of parabiotically paired rats resulted in suppression of gastrointestinal motility in the recipient as well as the donor. Since the parabiotic rats are joined only through their circulatory system (no neurological bridge exists), the effect of the intracerebral morphine given to the donor upon the gastrointestinal tract of the recipient could only be achieved by a neurohumoral agent transferred through the cross-circulating blood. These findings suggest that certain pharmacological properties attributed to the morphine molecule per se, may be due to an unique neuro-humor released from brain tissue.
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