Site-specific hydrogen sulfide-mediated central regulation of respiratory rhythm in medullary slices of neonatal rats

Abstract

Hydrogen sulfide (H2S) is involved in central regulation of respiratory rhythm at the level of the medulla oblongata. The present study was carried out to test our hypothesis that H2S exerts site-specific regulatory action on respiratory rhythm in the medulla oblongata of neonatal rats. The rhythmic discharge of hypoglossal rootlets in medullary slices of neonatal rats was recorded. 200μM NaHS (an H2S donor) increased burst frequency (BF) in 900-μm slices containing the pre-Bötzinger complex (preBötC), whereas it caused diphasic responses in 1200-, 1400- and 1800-μm slices containing both the preBötC and part or all of the parafacial respiratory group (pFRG): an initial decrease in BF followed by an increase. The initial decrease in BF was no longer observed after unilateral lesion of the pFRG region in the 1400-μm slices. In addition, BF was increased by a unilateral micro-injection of NaHS into the preBötC region, but was decreased by an injection into the pFRG region. These data support our hypothesis that the regulatory action of H2S on respiratory rhythm in the medulla oblongata is site-specific. The excitatory effect is caused by the preBötC, while the inhibitory effect is from the pFRG.