Autoradiographic demonstration of the central origin of regenerating fibers into iris tissue implants in the rat mesencephalon

Abstract

One model useful for demonstrating axonal regeneration in the central nervous system is that in which peripheral tissue, particularly the iris, is implanted into the brain or spinal cord. The aim of the present study was to establish the origin of some of the regenerating fibers by the use of an autoradiographic tracing technique. Briefly, iris implants were inserted in the caudal mesencephalon in the region of the dorsal tegmental bundle in unilaterally sympathectomized rats. Approximately two weeks later, subjects were injected with [ 3H]leucine in the region of the ipsilateral locus coeruleus and sacrificed two days later. Numerous labeled fibers were observed within the implants and traversing between brain and implant. Fibers formed loose plexuses, coursed along smooth muscle and grew toward blood vessels within the implants. These results may be added to fluorescent histochemical, biochemical and ultrastructural evidence supporting the regenerative capacity of central noradrenergic fibers.