An investigation of spontaneous potentials recorded from the smooth-muscle cells of the guinea-pig seminal vesicle.

1. A spontaneous discharge of small potentials from smooth muscle cells of the guinea-pig seminal vesicle has been described. The mean amplitude, frequency and duration of the potentials were 0.9 mV, 12.2/min, and 92 msec, respectively. Occasionally, large potentials of 5-7 mV were recorded.2. The frequency of spontaneous potentials was enhanced by about twofold in 15 mM potassium-Krebs solution. Removal of calcium from the perfusing solution, or adding excess magnesium (12 mM) suppressed the rate of these potentials. Cobalt (2.5 mM) did not affect them but blocked excitatory junction potentials evoked by the hypogastric nerve stimulation.3. The spontaneous potentials were unaffected by atropine. Their rate and amplitude were reversibly reduced in the presence of high concentrations of phentolamine (10(-4) but not by 10(-5) g/ml.). Guanethidine enhanced the frequency initially (5 min), but subsequently the control rate was not appreciably changed, even after 20 min of guanethidine perfusion.4. After post-ganglionic denervation or reserpine treatment, the frequency of discharge of spontaneous potentials was reduced, without any effect on amplitude.5. The properties of the spontaneous potentials recorded from the smooth muscle cells of the seminal vesicle are similar to those reported for the vas deferens. They appear to be due to an interaction between noradrenaline released from sympathetic nerve endings and the smooth-muscle cell membrane. Present experiments cannot completely rule out the possibility that another transmitter in addition to noradrenaline may be released at this neuroaffector junction.