This study examines the role of gap junctional communication in smooth muscle in relation to the frequency of stimulation and the innervation density of the tissue in the generation of neurogenic contractions. Towards this end the effects of heptanol, a gap junctional blocker, on the neurogenic contractions of guinea pig and rat vas deferens at different frequencies of stimulation (single pulse, 5, 10, 20, 40, 60 and 80 Hz) were studied. In both the prostatic and epididymal halves of these tissues, heptanol abolished the neurogenic contractions at the lower frequencies of stimulation. At higher frequencies, contractions were resistant to heptanol action. The effect of heptanol on the neurogenic contractions was found to decrease with increasing stimulation frequency. The neurogenic contractions of rat vas deferens were more resistant to heptanol than those of guinea pig vas deferens. Our data indicate that gap junctional communication is significant in the generation of neurogenic contractions in both guinea pig and rat vas deferens in a frequency dependent manner, and we discuss the mechanisms underlying these findings.

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