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Nerve growth factor stimulates the development of substance P in sensory ganglia.

The development of the putative neurotransmitter substance P (SP) in rat dorsal root ganglion (DRG) was defined in vivo. The sixth cervical DRG of newborn rats contained 70 pg of SP, and the ganglionic content increased 5.5-fold during the first 5 weeks of life. Forelimb amputation partially prevented the normal developmental increase of SP in the sixth cervical DRG destined to innervate that limb. Conversely, treatment with nerve growth factor (NGF) increased both ganglionic SP and total ganglion protein. Moreover, NGF administration prevented the failure of SP development that followed amputation, suggesting that NGF may mediate the limb-DRG interaction. However, treatment with antiserum to NGF failed to significantly inhibit development of ganglion SP. Consequently, neonatal ganglia may remain responsive to NGF, without requiring the protein for survival. SP appears to be an excellent index of the maturation of neurons in dorsal root ganglia.