Electrophysiological correlations with postjunctional supersensitivity

Several lines of evidence have been found which suggest that a partial depolarization is an important event in the development of postjunctional (nondeviation) supersensitivity in the vas deferens and atrium. In the vas deferens of the guinea pig, experiments with microelectrodes indicate that a depolarization of approximately 10 mV occurs after denervation or decentralization. The time course of the depolarization is the same as the time course of the development of supersensitivity found 7 days after denervation in the rat vas deferens. An analysis of the magnitude of junction potentials in the vas deferens supports the conclusion that changes in adrenergic receptors are not a significant factor in postjunctional supersensitivity. An analysis of membrane potential in guinea pig atria demonstrates a high correlation between the appearance of supersensitivity and a partial depolarization in that tissue alsomit is suggested that chronic interruption of the innervation to smooth or cardiac muscle leads to an alteration in the binding of calcium to the cell membrane and a consequent depolarization. The result is a resting membrane potential closer to the threshold for excitation.