NITRIC-OXIDE MODULATES RESPIRATORY-RELATED NEURAL ACTIVITY IN THE ISOLATED BRAIN-STEM OF THE BULLFROG

The effects of nitric oxide (NO) on respiratory-related neural activit y were investigated using the isolated brainstem preparation from bull frogs (Rana catesbeiana). Addition of the NO donor, sodium nitroprussi de (SNP), or the amino acid precursor for NO synthesis, L-arginine (L- Arg), produced significant increases in respiratory-related burst freq uency. Inhibition of nitric oxide synthase (NOS) with N-omega-nitro-L- arginine (L-NA), a non-selective NOS inhibitor,7-nitro indazole (7-NI) , reversibly abolished burst activity. These results suggest that prod uction of NO, probably via neuronal NOS (nNOS), provides a facilitator y input to the respiratory central pattern generator (CPG) in the amph ibian brainstem. Endogenous production of NO may be a necessary inter- or intracellular messenger for neurotransmission and/or neuromodulati on of central respiratory drive to motor effecters in the bullfrog. (C ) 1998 Published by Elsevier Science Ireland Ltd. All rights reserved.