Tetrahydro-beta-carboline may produce its stimulus effects via 5HT1B receptors

To further clarify the role of 5-hydroxytryptamine (5HT) in the behavioral effects of tetrahydro-beta-carboline, male rats were trained to discriminate either 20 mg/kg THBC from its vehicle (n = 10) or 2.0 mg/kg fenfluramine from saline (n = 5). THBC was observed to produce fenfluramine-like effects in the fenfluramine-trained rats while fenfluramine produced THBC-like effects in the THBC-discriminating rats. To investigate which of the serotonergic receptors may mediate the THBC-induced discriminative stimulus, various putatively specific 5HT agonists were administered to THBC-trained rats. Results indicate that the 5HT1B receptor agonists TFMPP and m-CPP substitute for THBC in a dose-response manner whereas 5HT1A agonists do not generalize to the THBC-induced discriminative stimulus. These observations support a role for the 5HT1B receptor site in the discriminative stimulus properties of THBC.