Stereospecific effects of d- and l-pentazocine on contractions of the mouse vas deferens.
The effects of the d- and l-isomers of pentazocine were compared to that of racemic pentazocine on contractions of the mouse isolated vas deferens. L-pentazocine inhibited electrically evoked contractions of the mouse vas deferens (MVD) in a dose-dependent manner (ID50 0.37 +/- 0.04 microM). In contrast, d-pentazocine augmented field stimulated contractions dose-dependently; per cent increases in contractions at 10 and 30 microM were 57.8 +/- 18.0 and 98.0 +/- 15.1%, respectively. Racemic pentazocine produced an intermediate effect between the two isomers. The effect of 1-pentazocine was antagonized by naloxone, whereas that of d-pentazocine was not. L-pentazocine did not effect the response of the MVD to exogenous norepinephrine at any concentration tested, while d-pentazocine depressed the response of the MVD to exogenous norepinephrine at one dose (0.3 microM). These findings demonstrate that d- and l-pentazocine produce opposite effects on the MVD. The effects of l-pentazocine are opioid mediated, while those of d-pentazocine are not. In the racemic mixture the opposing effects of the two isomers modulate each other, resulting in a diminished effect.
D000818:Animals; D004558:Electric Stimulation; D008297:Male; D051379:Mice; D009119:Muscle Contraction / Q000187:drug effects; D009270:Naloxone / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D010423:Pentazocine / Q000494:pharmacology*; D011957:Receptors, Opioid / Q000187:drug effects*; D013237:Stereoisomerism; D014649:Vas Deferens / Q000187:drug effects*
D011957:Receptors, Opioid; D009270:Naloxone; D010423:Pentazocine; D009638:Norepinephrine