Sympathetic innervation of the jejunal villus.

Using fluorescent histochemical methods it has been shown that the noradrenergic nerves in the jejunal villus are associated with the capillaries underlying the basolateral membrane of the epithelium. Noradrenergic fibres were also seen to lie between the epithelial basolateral membrane and the capillaries but were never observed close to the epithelium unless accompanied by an underlying capillary. The distribution of noradrenergic fibres suggests that it is unlikely that noradrenaline diffuses directly from the varicosity to the epithelial basolateral membrane. Noradrenaline may, therefore, act on the capillary itself and in some way affect fluid absorption. However, noradrenaline released adjacent to a capillary might diffuse into the capillary to be distributed at another site along its course.