Blockade of the stimulus properties of mescaline by a serotonin antagonist

It is known that the effects of mescaline (3, 4, 5-trimethoxyphenylethylamine), a hallucinogen, can function as a discriminative stimulus. The present investigation examined the ability of cinanserin, a serotinin antagonist, to block the stimulus properties of mescaline in the rat. After a reliable discrimination was established between the effects following the injection of mescaline (10 mg/kg) and those following administration of saline, subjects were pretreated with cinanserin HC1 (3 mg/kg) and then treated with mescaline. Such pretreatment was found to block discrimination, i.e., the response rate following the administration of mescaline plus cinanserin was appropriate for the saline condition. The present data suggest that antagonists of serotonin may be useful in furthering our understanding of phenethylamine hallucinogens.