Discriminative stimulus effects of panadiplon (U-78875), a partial agonistat the benzodiazepine site, in pentobarbital-trained rhesus monkeys

The pentobarbital-like discriminative stimulus effects of the benzodiazepin e receptor partial agonist panadiplon were assessed in rhesus monkeys train ed to discriminate pentobarbital (10 mg/kg) from saline. In test sessions, pentobarbital and the benzodiazepine full agonist triazolam engendered near 100% drug-appropriate responding in all monkeys, whereas panadiplon engend ered near 100% drug-appropriate responding in two of four monkeys. Panadipl on pretreatment resulted in leftward shifts in the pentobarbital dose-respo nse function but predominantly rightward shifts of the triazolam dose-respo nse function. These results are consistent with findings that benzodiazepin e partial agonists have pentobarbital-like discriminative stimulus effects in some subjects only, and further suggest that partial agonists enhance th e effects of pentobarbital but antagonize the effects of a benzodiazepine f ull agonist. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.