Actions of nitric oxide and expression of the mRNA encoding nitric oxide synthase in rat vagal afferent neurons.

The present study has investigated whether nitric oxide (NO) is involved in neurotransmission of rat vagal afferent neurons. The diethylamine-NO complex (diethylamine-NO, 10-100 microM) and S-nitroso-N-acetylpenicillamine (3-100 microM) both elicited a concentration-dependent depolarisation of the isolated rat nodose ganglion preparation. Pre-treatment with 1 H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 300 nM), 6-(phenylamino)-5,8-quinolinedione (LY83,583, 30 microM) and Methylene blue (100 microM) all caused a significant shift to the right in the concentration-response curve to diethylamine-NO. Incubation of rat nodose ganglion sections with a 35S-labeled antisense oligonucleotide to neuronal NO synthase resulted in visualisation of the mRNA encoding NO synthase over vagal afferent perikarya. The anatomical findings, therefore, suggest that a number of rat vagal afferent perikarya possess the ability to produce the enzyme required for the biosynthesis of NO. Collectively, these data suggest that NO may be functionally important as a neuromodulator of rat vagal afferent neurons.