Tyrosine Hydroxylase and NADPH-Diaphorase in the Rat Nodose Ganglion: Colocalization and Central Projection

Abstract

The present study was conducted to reveal the morphological characteristics of neurons of the nodose ganglion expressing nitric oxide synthase (NOS) and/or tyrosine hydroxylase (TH). The NADPH-diaphorase activity, a histochemical marker for NOS, was observed in 60% of ganglionic neurons, but TH-immunoreactivity shared only 8% of total ganglionic neurons. In this ganglion, 55% of Thimmunoreactive neurons expressed NADPHdiaphorase activity. By the triple combination of retrograde neuronal tracer (rhodamine labeled latex microspheres) injected into the rostral part of the nucleus tractus solitarius, the NADPH-diaphorase histochemistry and TH-immunocytochemistry, we found that 38% of NADPH-diaphorase positive neurons, 70% of TH-immunoreactive neurons, and 72% of NADPH-diaphorase/TH-positive neurons contained the rhodamine-latex fluorobeads. Thus, it is concluded that many of NOS and/or TH expressing neurons in the nodose ganglion centrally project primary sensory neurons.