The effects of chronic reserpine treatment on the contractile activity of the isolated vas deferens of the guinea pig.

Chronic reserpine treatment of guinea pigs during 5 days (1 mg/kg/day) induces postjunctional supersensitivity in the isolated vas deferens. It has been previously proposed that postjunctional supersensitivity occurs as a result of an ionic and/or membrane mechanism. Contrasting with previous observations in vascular smooth muscle the present results demonstrate that chronic reserpine treatment did not increase the sensitivity of the depolarized vas deferens to calcium. Experiments on drug responsiveness show that the supersensitive depolarized tissues have a greater and slower rate of loss of responsiveness than do control vasa deferentia. However, in a Ca2+-free Krebs solution responsiveness of supersensitive vasa deferentia did not differ from that of control tissues. These findings suggest that, in the guinea-pig vas deferens, reserpine-induced supersensitivity could be at least partially dependent on the increased availability of a calcium store(s) probably located at the cell membrane and/or cytoplasmic compartments.