The effect of different serotonin (5-HT) agonists and antagonists on the discriminative stimulus properties (cue) induced by 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OHDPAT), 1-(m-trifluoromethylphenyl)piperazine (TFMPP) and d-LSD (d-lysergic acid diethylamide) has been investigated. The 8-OHDPAT cue was mimicked by the 5-HT1A agonists ipsapirone, buspirone, gepirone and partially by...