Intrinsic innervation of the ewe cervix and its variations during pregnancy.

The course of the cholinergic and adrenergic nerve fibers in the cervix of the ewe was investigated in nonpregnant and pregnant animals using an acetylcholinesterase method and fluorescence histochemistry. Both technics in nonpregnant animals revealed a rich network of acetylcholinesterase and norepinephrine positive nerves around the blood vessels while the muscular innervation was moderately positive. Acetylcholinesterase fibers were also concentrated beneath the surface epithelium forming a plexus-like arrangement where isolated ganglion cells could be seen. At mid pregnancy cholinergic and adrenergic fibers decreased in density. The intensity of fluorescence was weaker and nerve fiber morphology was modified. We endeavoured to relate our findings to the problem of the neural control of contractions and the opening of the cervix of the ewe which is poorly supplied in nerve fibers, particularly at mid pregnancy.