BUSPIRONE, GEPIRONE, IPSAPIRONE, AND ZALOSPIRONE HAVE DISTINCT EFFECTS ON THE DIFFERENTIAL-REINFORCEMENT-OF-LOW-RATE 72-S SCHEDULE WHEN COMPARED WITH 5-HTP AND DIAZEPAM

The effects of four serotonin (5-HT)-1A compounds (buspirone, gepirone , ipsapirone and zalospirone) were compared with 5-hydroxytryptophan ( 5-HTP) [a 5-HT precursor with antidepressant (AD) efficacy], and diaze pam (a benzodiazepine anxiolytic), on a differential-reinforcement-of- low-rate 72-s (DRL 72-s) schedule. Past research has shown that AD and anxiolytic compounds each have distinct effects on the DRL 72-s inter response time (IRT) distribution profile. In the present paper, the pr ofile of the IRT distribution was quantitatively characterized by thre e metrics: burst ratio, peak location and peak area. 5-HTP shifted the IRT distribution peak toward longer IRT durations, increased reinforc ement rate and decreased response rate. The profile of the IRT distrib ution was not disrupted by 5-HTP. Diazepam disrupted the IRT distribut ion and increased bursting. In general, the arylpiperazine, 5-HT1A com pounds increased reinforcement rate, decreased response rate and disru pted the profile of the IRT distribution. The effects of the four aryl piperazine 5-HT1A compounds on the IRT distribution profile were diffe rent from the AD profile of 5-HTP and the benzodiazepine anxiolytic pr ofile of diazepam. Disruption of the IRT distribution by buspirone, ge pirone, ipsapirone and zalospirone may result from decreased 5-HT tran smission mediated by the presynaptic, somatodendritic 5-HT1A receptor.