Abstract
The potent circulatory effects of pentazocine have been investigated, and it is known that it may effect on the sympathetic nervous system of vascular smooth muscles. In the isolated mouse vas deferens, which are richly innervated by adrenergic nerve fibers, the effects of pentazocine on adrenergic transmission were studied and following results were obtained.
(1) On transmural stimulation (10HZ) biphasic mode (twitch-like and tetanus-like) of contraction was observed. Pentazocine (10-7M-3×10-5M) potentiated tetanus-like contraction dosedependently.
(2) The contraction produced by stimulation of norepinephrine (NE) (8×10-7M) was not potentiated by pentazocine (3×10-6M) .
(3) On the study of the overflow of 3H-NE (2×10-7M, 15Ci/mM), pentazocine (10-7M-10-5M) had no effect on stimulation-induced overflow, but induced augmentation of the basal overflow dosedependently.
These results of experiments suggested that pentazocine pontentiated the sympathetic tone of the vas deferens. And increased spontaneous release of NE. The cumulative effects of NE released both spontaneously and by stimulation might produced the sympathomimetic effects of pentazocine.
