Primary Rat Trigeminal Neurons NADPH-d / NOS Distribution

Objective:To identify the NOS-containing structures of rat trigeminal primary afferent neurons, located in the trigeminal ganglion (TrG) and mesencephalic trigeminal nucleus (MTN). Method:Using nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) histochemistry and nitric oxide synthase (NOS) immunohistochemistry. Results:In the TG approximately most of the neuronal population was NADPH-d reactive. Strongly positive were neurons mainly of small-to-medium size. Neuronal profiles of large diameter were less intensely stained. In addition, NADPH-d-positive nerve fibers were dispersed throughout the ganglion. Nitrergic neurons were located in the caudal part and mesencephalic-pontine junction of the MTN. Most of them were large-sized pseudounipolar cells. In a more rostral aspect, the reactive psedounipolar MTN profiles gradually decreased in number and intensity of staining. There, only a fine meshwork of stained thin fibers and perisomatic terminal arborizations, and also some isolated perikarya of NADPH-d stained multipolar MTN neurons, were observed. Conclusion:Differential expression patterns of NADPH-d suggest that trigeminal sensory information processing in the rat TG and MTN is controlled by nitrergic input through different mechanisms. NO may play a role in the pain transmission and proprioceptive information from the orofacial in the rat trigeminal afferent pathways.