The interaction between prostaglandin E1 and? 9-Tetrahydrocannabinol on intestinal motility and on the abdominal constriction response in the mouse

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Abstract
The interaction betweenΔ 9-tetrahydrocannabinol (THC) and PGE1 was studied using two pharmacological parameters-the rate of passage of a charcoal meal through mouse small intestine and the abdominal constriction response in the mouse. PGE1 administered intraperitoneally produced a dose-dependent decrease in intestinal motility, and this effect was antagonized by low (0.25 mg/kg) doses of THC and potentiated by higher doses of THC (1 mg/kg). Kinetic analysis suggested that the interaction was of a mixed but predominantly competitive type. PGF2α produced an increase in intestinal motility but this was not dose-dependent. THC antagonized the effect of PGF2α in a dose-dependent manner suggestive of a physiological antagonism. THC (0.25–2 mg/kg) antagonized the dosedependent PGE1 abdominal constriction response in a fashion which suggested a mixed (though mainly competitive) antagonism. It would seem, therefore, that on the two pharmacological parameters studied THC appears to be interacting with PGE1 at the same receptor site. Although the doses of THC used are within the range of those used in man, it is not implied that these results are necessarily implicated in the psychoactivity of the drug.