Changes in the innervation and catecholamine concentrations in the myometrium of pregnant and non-pregnant sheep.

The innervation of the myometrium in virgin, pregnant and post-partum ewes was examined using the SPG histofluorescence method and a high-performance liquid chromatographic catecholamine assay. In non-pregnant ewes, fluorescent axons were visible in all regions of the uterus. At 50 days of pregnancy the innervation was unchanged, but at 100 days axons were scarce over the whole uterus with the exception of the tubal extremities of the uterine horns. Noradrenaline concentrations were also significantly lower in late pregnancy, and significant variations occurred in different regions of the uterus, with the greatest concentrations present in the tubal extremities. At 13-16 weeks post partum, the density of innervation was variable, although the noradrenaline concentration was only slightly less than in virgin animals. Dopamine was also present in substantial quantities, but the mean concentrations remained unchanged during pregnancy.