LOCALIZATION OF BASIC FIBROBLAST GROWTH-FACTOR (BFGF)-LIKE IMMUNOREACTIVITY IN NEURAL CIRCUITS INNERVATING THE GASTROCNEMIUS-MUSCLE, WITH REFERENCE TO THE DIRECTION OF BFGF TRANSPORT

An antiserum against basic fibroblast growth factor (bFGF), characteri zed by immunoblot, was firstly used to immunolocalize bFGF-like materi als in dorsal root ganglion (DRG) neurons, spinal motoneurons and thei r processes innervating the gastrocnemius muscle, and then secondly to determine the direction of bFGF transport in the processes by nerve l igation or nerve section experiments. Light and electron-microscopic i mmunohistochemistry revealed that significant numbers of DRG neurons ( mainly of the large type), spinal motoneurons and their processes supp lying the muscle are immunoreactive for bFGF, and that the bFGF neuron s have diffuse immunoreaction deposits over the entire cytoplasmic are as except for the Golgi complex, mitochondria and microfilaments. Nerv e terminals and glial processes with bFGF were rarely seen in contact with or in close apposition to the immunopositive neurons. At sixteen hours, 3 days and 7 days after unilateral ligation or transection of t he sciatic nerve, bFGF fibers accumulated in a time-dependent way in t he proximal but not in the distal stump; nerve transection caused a mo re intense accumulation of bFGF-immunoreactive fibers than did nerve l igation. These findings suggest that bFGF in large DRG neurons and mot oneurons is transported anterogradely into the peripheral tissue, poss ibly without being incorporated into secretory granules or synaptic ve sicles. They raise the possibility that bFGF within the transected ner ve fibers is more actively conveyed during regeneration than in the li gated nerve fibers.