Growth of medial forebrain bundle axons into peripheral nerve grafts in the rat

In rats, we intercepted medial forebrain bundle axons just lateral to the hypothalamus with peripheral nerve grafts which terminated extracranially. The neurons which grew into the nerve grafts were labeled with retrogradely transported fluorescent dyes. Catecholamines were labeled with glyoxylic acid histofluorescence. Most nuclei, particularly the raphe complex and locus coeruleus, which project rostrally into the medial forebrain bundle were labeled. Many catecholamine fibers were observed in the graft even after removal of the superior cervical ganglions. Thus, monoaminergic neurons which were located relatively remotely from the implant site exhibited rather selective regrowth into the nerve grafts.