The relationship between innervation and arterial structure in late prenatal and early postnatal development of the rat jejunal artery.

The peripheral nervous system exerts a trophic influence on target tissues. We have examined the development of the perivascular innervation of the rat jejunal artery and correlated the simultaneous development of the endothelium and medial smooth muscle. Before birth a close relationship exists between endothelial cells and the first layer of differentiating medial smooth muscle, whereas the nerve fibres at this stage are formed into large remote bundles. After birth the differentiation of the media continues and the endothelial cells become separated from the smooth muscle by a thick internal elastic lamina. The nerve fibres grow from the large peripheral bundles to reach the smooth muscle as small bundles or individual fibres, with those immunoreactive to anti-calcitonin gene-related peptide being best developed by birth. From these studies it would seem that it is unlikely that perivascular nerve fibres influence the early development of the arterial wall, but they suggest that endothelial cells are more likely to be involved.