Effects of concomitant pentazocine and tripelennamine on brain-stimulation reward

Reinforcing thresholds for self-stimulation behavior to the medial forebrain bundle were determined in rats by means of a rate-free psychophysical method. The acute administration of either pentazocine or tripelennamine caused a small but significant lowering of the reward threshold. Combined administration of an ineffective dose of tripelennamine with various doses of pentazocine resulted in a potentiation of this lowering effect. These results suggest that the widespread abuse of the combination of pentazocine and tripelennamine may be due to a pharmacologic potentiation rather than just a summation of their two effects.