Variation of postjunctional natures along the length of the rat vas deferens as a cause of regional difference in the sensitivity to norepinephrine.

Sensitivity to norepinephrine (expressed as pD2) was different between the prostatic and the epididymal half of the rat vas deferens. The epididymal half was more sensitive than the prostatic half; difference in pD2 was 0.826 +/- 0.095 (mean +/- S.E., 13 experiments). Between the two halves, nearly the same difference in pD2, 0.745 +/- 0.125 (6 experiments), was observed in the responses to methoxamine, which is not incorporated into the adrenergic nerve terminals. In the two halves, 3 x 10(-6) M phentolamine produced a smiliar decrease in pD2 of norepinephrine: 1.485 +/- 0.056 and 1.282 +/- 0.080 in the prostatic and epididymal half, respectively (6 experiments). Only in the prostatic half, 10(-5) M propranolol produced a slight increase in pD2 of norepinephrine, 0.344 +/- 0.133 (6 experiments). Sensitivity to K+ was also different between the two halves. These results suggest that the difference in the sensitivity to norepinephrine between the prostatic and the epididymal half is due to postjunctional natures varying along the length of the rat vas deferens.