EFFECT OF GROWTH-FACTORS ON SUBSTANCE-P MESSENGER-RNA EXPRESSION IN AXOTOMIZED DORSAL-ROOT GANGLIA

THE effects of NGF, BDNF, NT-3, BDNF plus NT-3 and LIF on substance P (SP) mRNA levels were analysed in axotomized dorsal root ganglia (DRGs ) in vivo by quantitative in situ hybridization. The growth factors we re applied on to the transected sciatic nerve. SP mRNA levels were dec reased significantly 3 days after axotomy. NGF (1 mu g) fully countera cted the down-regulation of SP mRNA. Neither BDNF (10 mu g) nor NT-3 ( 10 mu g) alone had any effect. However, co-administration of BDNF toge ther with NT-3 (10 mu g) distinctly reversed the decrease in SP mRNA. A similar effect was seen with a high (1.5 mu g) but not a low dose of LIF (0.15 mu g). Our data suggest that the present method of deliveri ng growth factors to the transected sciatic nerve is a valid way to st udy in vivo effects of growth factors on peptide expression in DRGs. M oreover, SP expression is regulated by several growth factors in vivo such as NGF, BDNF plus NT-3 as well as the neuroimmune factor LIF.