Different effects of respiratory and metabolic acidosis on preganglionic sympathetic nerve activity

metabolic acidosis on preganglionic sympathetic nerve activity. J. Appl. Physiol. 77(l): 173-178, 1994.-We studied sympa-thetic nerve activity (SNA) responses, recorded in multifiber preparations of left third thoracic white ramus, to respiratory or isocapnic metabolic acidosis or to CO, enhancement at con-stant pH in chloralose-anesthetized paralyzed artificially ven-tilated cats. Cardiopulmonary, baro-, and peripheral chemore-ceptors were denervated by bilaterally cutting vagus and ca-rotid sinus nerves. Acidosis was induced by either decreasing artificial ventilation or infusing HCl (0.5 M iv). Both respira-tory and isocapnic metabolic acidosis induced a decrease in lo-cal extracellular pH, measured directly with pH-sensitive mi-croelectrodes within medulla region containing sympathoexci-tatory bulbospinal neurons. The magnitude of changes in medullary pH was independent of the way systemic acidosi