Modulation of Morphine Action by Lauric Acid

Abstract

Intraperitoneal administration of lauric acid (C₁₂) at the high doses, 100-1000μmol/kg, showed weak but dose-dependent antinociceptive effect in mice. Pretreatment of the animals with 0.1μmol/kg of i.p. C₁₂ tended to suppress the antinociceptive effect of 7mg/kg of s.c. morphine and daily combination of this dose of C₁₂ with 10mg/kg of s.c. morphine blocked the development of antinociceptive tolerance to morphine. However, increasing or decreasing of the dose of C₁₂ resulted in the loss of its modulatory effect on morphine. The strict dose-dependency of C₁₂ in its action on morphine suggests that there is a regulatory role for C₁₂, a medium length straight chain fatty acid, in the endogenous pain inhibitory system.