Postnatal ontogeny of the neurotrophin receptors trk and trkB mRNA in rat sensory and sympathetic ganglia.

Using reverse transcription followed by polymerase chain reaction, we examined the expression of mRNA for the tyrosine kinase receptors trk and trkB in rat sensory and sympathetic ganglia during postnatal development. While the levels of both trk and trkB mRNA in the dorsal root ganglia (DRG) decreased two-fold, they increased by seven and two times, respectively, in superior cervical ganglia. The developmentally regulated and tissue-specific expression of trk and trkB genes suggest that peripheral ganglia differ in their responsiveness to neurotrophins in neonatal and adult rats. We found that the temporal pattern of trk expression in DRG neurons correlates with the observed age-dependent ability of nerve growth factor to induce the biosynthesis of the neuropeptide substance P.