Mechanisms involved in electrically-induced responses of rat seminal vesicles

Contractile responses of rat isolated seminal vesicle were elicited by electrical field stimulation (EFS, 10 Hz, 1 ms, 40 V for 5 s), noradrenaline (1 x 10(-5) M) and carbachol (1 x 10(-5) M). Guanethidine (2 x 10(-5)-5 x 10(-4) M) progressively reduced the contraction induced by EFS and carbachol to 24 +/- 2 and 10 +/- 2%, respectively, at the highest concentration (n = 6), while potentiating noradrenaline contraction to a maximum of 154 +/- 14% at 2 x 10(-5) M (n = 6). Prazosin (1 x 10(-6) M) and atropine (2.5 x 10(-7) M) completely abolished the response to the corresponding agonist and each reduced the response to EFS to 64 +/- 8 and 61 +/- 3%, respectively (n = 6). In the presence of both atropine and prazosin a small contraction to EFS remained (14 +/- 4%, n = 6), which is unlikely to be due to ATP, since exogenous ATP did not induce a contractile response and had an inhibitory effect on EFS-induced responses. Clonidine (1.25 x 10(-5) M) completely blocked responses to noradrenaline and reduced the responses to EFS to 68 +/- 7% (n = 6). However, when both the adrenergic and cholinergic components of EFS were blocked by prazosin and atropine, clonidine potentiated the remaining response to EFS (323 +/- 82%, n = 4). Yohimbine (1 x 10(-5) M) blocked the response to noradrenaline and reduced the response to EFS to 37 +/- 5% (n = 6) while the carbachol response was unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)