Development of tolerance to the antinociceptive effect of mescaline intraventricularly administered to rabbits

In conscious rabbits, acute intraventricular injection of mescaline at doses of 70, 100, and 150 micrograms per kilogram produced dose-dependent analgesia, measured by electrical stimulation of the tooth pulp. With daily administration of 100 micrograms per kilogram for five days, complete tolerance developed to this antinociceptive effect. Tolerance also developed to the behavioral effects of mescaline after repeated doses, except for a stuporous state, which became more pronounced as treatment continued. Acute mescaline caused EEG arousal; chronic treatment at 100 micrograms per kilogram progressively slowed the return of voltage to original levels. Comparing certain mescaline-induced effects with those of morphine suggests some shared biochemical and neural patterns.

Study at a glance

Abstract

Some effects of intraventricular injection of mescaline are examined in conscious rabbits. By means of electrical stimulation of the tooth pulp it is shown that an acute treatment with 70, 100, 150 mug/kg of mescaline elicits analgesia, the intensity of which is dose-dependent: with daily administration of 100 mug/kg for 5 days a complete tolerance develops to the antinociceptive effect. A tolerance also develops to the behavioral effects of mescaline after repeated administrations, with the exception of the stuporous state, a symptom which, on the contrary, is accentuated as the treatment proceeds. An EEG arousal is induced in the rabbit by acutely administered mescaline; the chronic treatment (100 mug/kg) makes the return of voltage to original levels progressively slower. Finally, the confrontation of certain of the mescaline-induced effects with those of morphine suggests some biochemical and neural patterns common to the 2 drugs.