SITE-SPECIFIC HYDROGEN SULFIDE-MEDIATED CENTRAL REGULATION OF RESPIRATORY RHYTHM IN MEDULLARY SLICES OF NEONATAL RATS

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. 200 mu M NaHS (an H2S donor) increased burst frequency (BF) in 900-mu m slices containing the pre-Botzinger complex (preBotC), whereas it caused diphasic responses in 1200-, 1400- and 1800-mu m slices containing both the preBotC 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-mu m slices. In addition, BF was increased by a unilateral micro-injection of NaHS into the preBotC 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 preBotC, while the inhibitory effect is from the pFRG. (c) 2012 IBRO. Published by Elsevier Ltd. All rights reserved.