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. 2011;22(4 Suppl):174-86.
doi: 10.1353/hpu.2011.0168.

Intracellular acidosis and pH regulation in central respiratory chemoreceptors

C R Marutha Ravindran  1 , James N Bayne, Sara C Bravo, Theo Busby, Charles N Crain, John A Escobedo, Kenneth Gresham, Brian J O'Grady, Lourdes Rios, Shashwata Roy, Matthew J Gdovin
Affiliations

Intracellular acidosis and pH regulation in central respiratory chemoreceptors

C R Marutha Ravindran et al. J Health Care Poor Underserved. 2011.

Abstract

Dysfunctions of brainstem regions responsible for central CO2 chemoreception have been proposed as an underlying pathophysiology of Sudden Infant Death Syndrome (SIDS). We recorded respiratory motor output and intracellular pH (pHi) from chemosensitive neurons in an in vitro tadpole brainstem during normocapnia and hypercapnia. Flash photolysis of the H+ donor nitrobenzaldehyde was used to induce focal decreases in pHi alone. Hypercapnia and flash photolysis significantly decreased pHi from normocapnia. In addition, chemoreceptors did not regulate pHi during hypercapnia, but demonstrated significant pHi recovery when only pHi was reduced by flash photolysis. Respiration was stimulated by decreases in pHi (hypercapnia and flash photolysis) by decreases in burst cycle. These data represent our ability to load the brainstem with nitrobenzaldehyde without disrupting the respiration, to quantify changes in chemoreceptor pHi recovery, and to provide insights regarding mechanisms of human health conditions with racial/ethnic health disparities such as SIDS and Apnea of Prematurity (AOP).

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Figures

Figure 1
Figure 1
pHi profiles from three representative neurons located in chemosensitive regions from a developmental stage 11 tadpole during hypercapnia, normocapnia, and flash photolysis of UV light (downward arrow). pHi during hypercapnia was significantly lower than during normocapnia and the decreases in pHi attained by uncaging H+ were significantly lower than pHi during normocapnia. Note that during hypercapnia the pHi shows no sign of recovery, as both intracellular and extracellular pH are reduced, however when only pHi is reduced using flash photolysis all three neurons demonstrate significant regulation of pHi.
Figure 2
Figure 2
Mean changes in gill burst respiratory variables during hypercapnic acidosis (HA) and UV flash photolysis (UV) normalized to normocapnia (NC). n=5 *indicates slightly different from normocapnia
Figure 3
Figure 3
Mean changes in lung burst respiratory variables during hypercapnic acidosis (HA) and UV flash photolysis (UV) normalized to normocapnia (NC). n=5 *indicates slightly different from normocapnia
See this image and copyright information in PMC

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