Response of isolated muscle of the human cervix to electrofield stimulation.

Contractile activity was registered isometrically in isolated strip biopsies from the uterine cervix of nonpregnant, early pregnant and term pregnant women, and the influence of electrofield stimulation (EFS) was studied. In the great majority of women an excitatory effect was observed, but occasionally an inhibitory response occurred. The excitatory effect of EFS was reduced and, in many cases, changed to inhibition during treatment with guanethidine and phenoxybenzamine. These inhibitory effects were not antagonized by treatment with propranolol, indicating that the responses were not mediated by beta-adrenoceptors. Tetrodotoxin reduced or abolished the excitatory effect of EFS. The data suggest that contractile activity of the human cervix is influenced by both adrenergic and nonadrenergic neurons, which remain intact throughout pregnancy. This innervation may be a central part of neuromuscular control systems which undergo important adaptive changes during pregnancy and in connection with parturition.