PRESENCE AND LOCALIZATION OF NEUROTROPHIN RECEPTOR TYROSINE KINASE (TRKA, TRKB, TRKC) MESSENGER-RNAS IN VISCERAL AFFERENT NEURONS OF THE NODOSE AND PETROSAL GANGLIA

The presence of mRNAs to the high affinity tyrosine kinase (Trk) recep tors for neurotrophins was studied in visceral afferent neurons of the nodose and petrosal ganglia of adult and neonatal rats using in situ hybridization histochemistry. Neurons containing TrkA mRNA were found in the adult nodose and petrosal ganglia. About 10% of nodose ganglion neurons and 38% of petrosal ganglion neurons contained TrkA mRNA. The nodose and petrosal ganglia from 1 day old neonates also expressed Tr kA mRNA. No TrkB mRNA-containing neurons were detected in the adult no dose and petrosal ganglia, whereas TrkB mRNA was detected in 1 day old neonatal nodose and petrosal ganglia. TrkC mRNA was found in about 9% of nodose ganglion neurons and 11% of petrosal ganglion neurons of ad ult rats. Likewise, low but detectable levels of TrkC mRNA were seen i n 1 day old neonatal nodose and petrosal ganglia. These data demonstra te the presence of TrkA and TrkC in the adult nodose and petrosal gang lia and provide a substrate for the ongoing neurotrophin-induced regul ation of these placodally derived visceral afferent neurons. The alter ed expression of Trk receptor mRNAs in the nodose and petrosal ganglia between the adult and neonatal rats may reflect developmentally regul ated changes in neurotrophin responsiveness.