Discriminative stimulus properties of the atypical neuroleptic clozapine in rats: tests with subtype selective receptor ligands

The interoceptive stimulus induced by clozapine (5 mg/kg, i.p.) has been characterized in an operant drug discrimination procedure in the rat using a wide range of receptor subtype-selective agonists and antagonists. Only the muscarinic receptor antagonist scopolamine generalized fully to clozapine (> 80%). Partial generalization (defined here as 40% maximal generalization) was seen with the Di receptor antagonist SCH 23390 (43% maximal generalization), the α1 -adrenoceptor antagonist prazosin (67%) and the α2-adrenoceptor antagonist methoxyidazoxan (42%). All other specific agents tested induced