CENTRAL TERMINALS OF OROFACIAL PRIMARY AFFERENTS AND NADPH-DIAPHORASEACTIVITY IN THE TRIGEMINO-SOLITARY COMPLEX OF RATS

Nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) activ ity and the central terminal fields of branches of the mandibular and chorda tympani nerves were visualized histochemically at the same time using transganglionic transport of wheat germ agglutinin conjugated w ith horseradish peroxidase. The blue NADPH-d-positive neurons comprise d a sparse network in the dorsomedial spinal trigeminal subnucleus ora lis and a dense one in the rostral lateral division of the nucleus of the solitary tract. In the subnucleus caudalis, most labeled neurons w ere in the superficial zone, and smaller numbers were in the magnocell ular zone. The NADPH-d-positive neurons in the subnucleus oralis and t he nucleus of the solitary tract overlapped mostly with the transgangl ionically labeled terminal field from the lingual nerve, partly with t he terminal field from the inferior alveolar and chorda tympani nerves , and rarely with the terminal field from the mental nerve. The NADPH- d-positive neurons in the dorsomedial paratrigeminal nucleus and subnu cleus caudalis overlapped mostly with the terminal field from the ling ual nerve, partly with the terminal field from the inferior alveolar a nd mental nerves and never with the terminal field from the chorda tym pani. A statistically significant reduction in the number of NADPH-d-p ositive neurons was seen bilaterally in subnucleus oralis and the nucl eus of the solitary tract when the lingual nerve was transected. Infla mmatory insults to the lingual nerve or tooth pulps significantly incr eased the number of NADPH-d-positive neurons in subnucleus oralis, the nucleus of the solitary tract, and subnucleus caudalis. These results show that the NO/cyclic GMP system in the trigeminal and solitary nuc lei is differentially regulated trans-synaptically by trigeminal affer ents depending on the nucleus and sensory modality. (C) 1998 Elsevier Science B.V.