Effects of nalbuphine alone and in combination with tripelennamine on rewarding brain stimulation thresholds in the rat.

Reinforcing thresholds for rewarding brain stimulation to the medial forebrain bundle-lateral hypothalamus were determined in rats by means of a rate-free psychophysical method. Nalbuphine, a mixed agonist-antagonist opioid, alone caused a significant, but modest, dose-dependent lowering of the threshold for reinforcing stimulation. Concomitant administration of an ineffective dose of tripelennamine, an antihistamine, with nalbuphine potentiated the threshold lowering effect of nalbuphine. These results are similar to previous results obtained with tripelennamine and pentazocine suggesting that nalbuphine may have abuse potential if combined with tripelennamine.