LOCALIZATION, DIFFERENTIAL EXPRESSION AND RETROGRADE AXONAL-TRANSPORTSUGGEST PHYSIOLOGICAL-ROLE OF FGF-2 IN SPINAL AUTONOMIC NEURONS OF THE RAT

Fibroblast growth factor-2 (FGF-2) has marked pharmacological neurotro phic effects on lesioned spinal autonomic neurons following target rem oval of the adrenal medulla, yet expression and axonal transport in au tonomic neurons remain to be shown. We show here FGF-2 and FGF recepto r type 1 (FGFR1) protein and mRNA expression in preganglionic intermed iolateral neurons of the rat thoracic spinal cord. While immunoreactiv ity of both FGF-2 and FGFR1 co-localize to intermediolateral neurons, mRNA transcripts of FGFR1, but not of FGF-2, are detectable in interme diolateral preparations by RNase protection analysis, suggesting prote in translocation in vivo. Unilateral microinjection of (125)iodinated FGF-2 into the adrenal medulla (a major target of intermediolateral ne urons) results in significant accumulation of specific radioactivity i n thoracic spinal cord tissue, including the intermediolateral neurons , and the ipsilateral splanchnic nerve. Emulsion autoradiography demon strated labelling over ipsilateral intermediolateral neurons only. Neu ronal co-localization of FGF-2/FGFR1 protein, differential mRNA expres sion, specific retrograde axonal transport and the known neurotrophic actions in vivo, strongly suggest unique physiological roles of FGF-2 in the autonomic nervous system.