ABSTRACT
OBJECTIVE: To identify the role of soluble guanylyl cyclase-cyclic guanine monophosphate (sGC-cGMP) pathway in the carbon monoxide (CO) mediating regulation of respiratory rhythm from the medulla oblongata. METHODS: Medullary slices of newborn Sprague-Dawley rats were prepared for the experiment. The electrophysiological experiment comprised 5 groups (each with 8 slices), each of which were perfused with artificial cerebrospinal fluid (ACSF control group), CO (exogenous CO group), 1H-[1,2,4] oxadiazolo [4,3-a] quinoxalin-1-one (a specific inhibitor of sGC, ODQ group), ODQ+CO (ODQ+CO group), and dimethyl sulfoxide (vehicle of ODQ, DMSO group), respectively. The burst frequency (BF) of hypoglossal rootlets was recorded as an index of rhythmic respiratory activity. Radioimmunoassay was employed to determine cGMP levels of the medullary slices of the ACSF control group, exogenous CO group, ODQ group and ODQ+CO group (n=6/ group). RESULTS: The exogenous CO decreased the BF (P < 0.05) and increased the cGMP level (P < 0.05). The ODQ increased the BF (P < 0.05) and decreased the cGMP level (P < 0.05). No significant changes were found in the BF and cGMP levels when CO and ODQ applied simultaneously (P > 0.05), but the BF increased (P < 0.05) after the drug perfusion ended. CONCLUSION: sGC-cGMP pathway may play an important role in the CO mediated regulation of respiratory rhythm from the medulla oblongata.