Cross tolerance to antinociception elicited by intracerebroventricular administration of mescaline and morphine to rabbits, and EEG correlates.

Tolerance and cross tolerance to the antinociceptive effect of equipotent doses of morphine (10 mug/kg) and mescaline (100 mug/kg) are shown in the rabbit after their repeated intracerebroventricular administration. The recording of the electrical activity of different brain areas indicates that a partial tolerance also develops to the EEG effects in animals undergoing chronic treatment with mescaline. The comparison of certain of the mescaline-induced effects with those of morphine suggests that some biochemical and neural patterns are common to the 2 drugs.