Effects Of (1)-Pentazocine on the Antinociceptive Effects of (-)-Pentazocine in Mice

Previous studies have shown that sigma-1 receptor chaperone (Sig-1R) ligands can regulate pain-related behaviors, and Sig-1R itself can regulate -opioid receptor functions as well as signal transduction. Even though (+/-)-pentazocine has been used clinically for the treatment of pain through opioid receptors, (+)-pentazocine is known to be a selective Sig-1R agonist. To the best of our knowledge, there is no information available regarding the involvement of Sig-1R agonistic action in the antinociceptive effects of (+/-)-pentazocine. Therefore, the present study was designed to investigate the effects of (+)-pentazocine on the antinociceptive effects of (-)-pentazocine in mice. Both and (-)-pentazocine induced biphasic antinociceptive effects as measured by the warm-plate test. The early phase, but not the delayed phase, of the antinociceptive effects induced by (-)-pentazocine, which are mediated by the activation of -opioid receptors, were suppressed by pretreatment with (+)-pentazocine. These results suggest that the innate antinociceptive action of (+/-)-pentazocine could be marginally reduced by the effects of (+)-pentazocine, but (+)-pentazocine can suppress the antinociceptive effects of (-)-pentazocine at certain time points. Synapse 69:166-171, 2015. (c) 2015 Wiley Periodicals, Inc.