Stimulus generalization of 1-(3-trifluoromethylphenyl)piperazine (TFMPP) to propranolol, pindolol, and mesulergine.

Using standard operant procedures with rats trained to discriminate the serotonin (5-HT) agonist 1-(3-trifluoromethylphenyl)piperazine (TFMPP) (0.5 mg/kg) from saline, tests of stimulus generalization and stimulus antagonism were conducted with propranolol, pindolol, and mesulergine. Neither propranolol nor mesulergine antagonized the TFMPP stimulus (pindolol was not evaluated as an antagonist). However, TFMPP-stimulus generalization occurred with all three agents. These results suggest that the TFMPP-stimulus may involve both a 5-HT1B and a 5-HT1C mechanism and further suggest that propranolol, pindolol, and mesulergine may be capable of acting as agonists at certain populations of serotonin receptors.