Fibroblasts and sympathetic innervation of blood vessels.

The distances between fibroblasts and adrenergic varicosities were measured in four distinct blood vessels of the dog, concomitantly with the measurement of corresponding distances between smooth muscle cells and adrenergic varicosities. The results showed a closer anatomical relationship between fibroblasts and adrenergic varicosities as compared to that of adrenergic varicosities and smooth muscle cells. These morphological results indicate that sympathetic neurotransmitter(s) may attain at the fibroblast membrane concentrations similar to those occurring at the smooth muscle cell membrane.