Pharmacological characteristics of contractile responses of rabbit uterine cervices to electrical field stimulation.

The pharmacological characteristics of contractile responses to electrical field stimulation (EFS) of uterine cervical muscular strips taken from non-pregnant and pregnant rabbits were investigated, in vitro. The contractile responses to EFS of both non-pregnant and pregnant muscular strips were markedly depressed by treatment with prazosin 1 microM, while the responses were only slightly depressed by treatment with atropine 1 microM. Propranolol 1 microM did not affect the responses. Guanethidine 10 microM and tetrodotoxin (TTX) 10 microM also depressed the contractile responses to EFS of both non-pregnant and pregnant muscular strips. However, the depressive effects of the latter 2 drugs were more marked in non-pregnant muscular strips than in pregnant ones. These findings indicate that the uterine cervical smooth muscle is predominantly innervated with adrenergic excitatory nerve fibers. The cholinergic innervation in uterine cervical smooth muscle seems minor. Furthermore, during pregnancy, a TTX-resistant, non-adrenergic, non-cholinergic component might increase the contractile response of uterine cervical smooth muscle to EFS.