Failure of non-adrenergic transmission in the rat vas deferens

Repetitive field stimulation of the vas deferens of the rat with long trains of pulses (90 pulses, 10 Hz, 1 msec) at intervals of 30 or 60 sec produced a decline in the heights of contractile responses. This decline in responses was much more pronounced in phentolamine (5 microM)-treated than in untreated preparations and in the prostatic rather than in the epididymal end of the vas deferens. The decline in the responses was dependent on the number of pulses/train, the frequency of pulses in the train and the interval between successive trains. Potassium chloride (KCl)-induced and adenosine triphosphate (ATP)-induced contractions were largely unaltered after 30 min of stimulation. The decline in the responses was significantly reduced in low but not in high extracellular calcium. 4-Aminopyridine (4-AP) caused an initial potentiation of contractile responses, followed by a faster decline of responses. The decline in responses was more intense in vas deferens from reserpine-treated animals. The results support the view that electrical stimulation-induced decay of motor transmission in the vas deferens of the rat is caused by a specific failure of the non-adrenergic transmission.