Denervation supersensitivity to norepinephrine in the guinea-pig vas deferens in vivo and in vitro: influence of the bathing solution.

After seven days of denervation there was a 10.7-fold increase in sensitivity without a significant alteration of the maximum response to norepinephrine (NE) in the guinea-pig vas deferens, in vivo. On the second postoperative day there was a significant increase in sensitivity and a decrease of the maximum response to NE in experiments performed in vivo. In the isolated guinea-pig vas deferens, immersed in Kreb's-Henseleit solution, an increased sensitivity to NE was demonstrable after two and seven days of denervation. However, an increased maximum response to NE was demonstrable only after seven days of denervation. Using McEwen solution there was no significant increase in the maximum response to NE in the seven-days denervated guinea-pig vas deferens. Slight alterations of the ionic composition of the physiological salt solutions prevented the demonstration of denervation-induced augmentation of the maximum response to NE in the isolated guinea-pig vas deferens. The characteristics of cocaine-induced supersensitivity to NE in the isolated guinea-pig vas deferens did not differ in vivo and were not affected by small changes in the ionic composition of the bathing solution. The absence of a postjunctional component of denervation supersensitivity to NE in the guinea-pig vas deferens, in vivo, is suggested. Furthermore, the demonstration of the postjunctional component of denervation supersensitivity to NE in the isolated guinea-pig vas deferens appears to be dependent of the composition of the bathing solution used.