The sympathetic neural apparatus of the rat uterus during the sexual cycle.

A microspectral fluorescence-histochemical method was used to study the sympathetic neural apparatus of the rat uterus at different phases of the sexual cycle. Most nerve fibers, as perivascular plexuses and terminals emanating from them, were located in the myometrium. It is suggested that the uterus contains reserve ("silent" nerve fibers, which explains the variability in their appearance in this organ. Microspectrofluorimetric studies identified catecholamines and serotonin in varicose swellings and intervaricosity segments of nerve fibers; levels at test points showed a strong linear correlation at all stages of the sexual cycle. The greatest bioamine levels in most structural elements of the sympathetic neural apparatus of the uterus were seen in late diestrus. Early and late estrus and proestrus were characterized by low monoamine levels in adrenergic fibers. A number of significant differences were seen between the level of saturation with bioamines and the spatial distribution density of nerve fibers in the body and cervix of the uterus.