Influence of castration on the membrane reactivity of the guinea-pig vas deferens.

The guinea-pig vas deferens is a quiescent muscle which after castration undergoes atrophy and shows spontaneous contractions preceded by membrane spike activity. The influence of castration on the spontaneous release of neurotransmitters and on the internal concentration of sodium and potassium ions was studied. Utilizing the microelectrode technique it was shown that castration induces a partial depolarization (10 mV) of the cell membrane, but did not change the frequency of spontaneous excitatory junction potentials (SEJPs) of guinea-pig vas deferens. However, the time-course and the amplitude of the SEJPs were increased after castration, probably because of changes in membrane properties related to organ atrophy. Castration probably promotes a change in the ionic permeability of the smooth muscle fibre, since the ratio pNa/pK was twice that of control muscles.