Functional responses of the rat isolated seminal vesicle to electrical field stimulation: a pharmacological analysis

1. Electrical field stimulation (EFS) of the rat isolated seminal vesicle elicited frequency-dependent and tetrodotoxin sensitive contractions which were unaltered by hexamethonium or mecamylamine. 2. Prazosin alone was not sufficient to abolish these responses, but a combination of atropine and prazosin was fully effective, indicating involvement of both noradrenergic and cholinergic mechanisms. 3. Responses were predominantly cholinergic (blocked by atropine, potentiated by ecothiopate but not significantly altered by prazosin or guanethidine) at 1-8 Hz but became increasingly noradrenergic (blocked by prazosin or guanethidine but relatively unaltered by atropine or ecothiopate) with increasing frequencies of stimulation. 4. Electrical field stimulation of seminal vesicles removed from reserpine or 6-hydroxydopamine (6-OHDA)-pretreated rats produced contractions that were clearly cholinergic in nature. 5. After exposing the seminal vesicles to guanethidine, or after pretreatment of rats with 6-OHDA, responses to EFS remained, indicating that activation of discrete cholinergic and noradrenergic innervations seem to underlie the contractile responses observed. 6. Yohimbine and prazosin potentiated the predominantly cholinergic responses at 1, 2 and 4 Hz in tissues from untreated rats, but not in those from animals pretreated with reserpine or 6-OHDA, indicating the possibility of an interaction between the two innervations. 7. No inhibitory responses to EFS could be demonstrated in tissues precontracted with KCl in the presence of a combination of atropine and prazosin suggesting the absence of a nonadrenergic, noncholinergic inhibitory innervation.