CHANGES IN NEURONAL CONTRIBUTION TO CONTRACTILE RESPONSES OF VAS-DEFERENS OF YOUNG AND ADULT GUINEA-PIGS

The response characteristics of vas deferens to electrical hypogastric nerve stimulation at various frequencies was studied in guinea pigs o f 2 to 15 weeks old. In 2-week-old guinea pigs the stimulation induced monophasic contraction, some of which remained after blocking alpha(1 )-adrenoceptor and desensitizing P-2-purinoceptors with prazosin and a lpha,beta-methylene ATP, respectively. In guinea pigs of 10 to 15 week s old stimulation induced biphasic contraction, which was almost compl etely inhibited by both blockers. These results suggest that some unkn own component other than ATP and norepinephrine is involved in the tra nsmission at 2 weeks, and that its relative significance changes durin g development.