PLASTICITY OF TYROSINE-HYDROXYLASE AND VASOACTIVE-INTESTINAL-PEPTIDE MESSENGER-RNAS IN VISCERAL AFFERENT NEURONS OF THE NODOSE GANGLION UPON AXOTOMY-INDUCED DEAFFERENTATION

The nodose ganglion contains placode-derived visceral sensory neurons of the vagus nerve. Previous study showed that axotomy-induced deaffer entation reduced the number of tyrosine hydroxylase-immunoreactive and increased the number of vasoactive intestinal peptide-immunoreactive neurons in the ganglion. The present study was conducted to determine whether the changes in neuropeptide/neurotransmitter enzyme content ar e associated with changes in the expression of tyrosine hydroxylase an d vasoactive intestinal peptide messenger RNAs in the nodose ganglion. We used in situ hybridization histochemistry with S-35-labeled oligon ucleotide probes for tyrosine hydroxylase and vasoactive intestinal pe ptide precursor messenger RNAs. Peripheral axotomy of visceral afferen t inputs reduced tyrosine hydroxylase messenger RNA and increased vaso active intestinal peptide messenger RNA expression in neurons of the n odose ganglion of the rat. The number of tyrosine hydroxylase messenge r RNA-containing neurons was significantly reduced at three, seven and 14 days after axotomy-induced deafferentation compared with intact an d sham-operated controls. Labeling density of tyrosine hydroxylase mes senger RNA-containing neurons was significantly reduced at three and s even days. Conversely, the number of vasoactive intestinal peptide mes senger RNA-containing neurons increased significantly al three, seven and 14 days, while the labeling density of vasoactive intestinal pepti de messenger RNA-containing neurons also increased at one, three, seve n and 14 days. The results of the present study indicate that the axot omy-induced down-regulation of tyrosine hydroxylase and up-regulation of vasoactive intestinal peptide in the neurons of the nodose ganglion are associated with changes in their messenger RNAs in response to ax otomy-induced deafferentation.