Autonomic innervation of preretinal blood vessels of the rabbit

The preretinal blood vessels, that is, blood vessels lying on the inner surface of the retina, were observed by SEM examination using digestion methods, TEM examination and fluorescence histochemical examination using the Falck-Hillarp method. The nerve endings on the preretinal arterioles were distributed from the optic disc to the periphery. The longest nerve terminals from the optic disc to peripheral arterioles were about 9 mm. There were also a few nerve endings on the preretinal veins. These nerve endings had a series of axonal varicosities with diameters between 0.5 and 1.5 mu, which contained empty synaptic vesicles and cored synaptic vesicles. The number of nerve endings on these arterioles decreased with the shortening of the diameter of the retinal arterioles. Fluorescent nerve fibers with axonal varicosities were distributed on the wall of the preretinal blood vessels in the fluorescence histochemical study. These fluorescent nerve fibers were numerous near the optic disc, but there were only a few fluorescent nerve fibers on the peripheral blood vessels. The nerve endings on the preretinal blood vessels disappeared following superior cervical ganglionectomy. The present study shows that the preretinal blood vessels in rabbit eyes are innervated by the sympathetic nerve originating from the superior cervical ganglion.