The Regulation of pH in an in vitro brainstem preparation of the bullfrog tadpole, Lithobates catesbeianus by central respiratory chemoreceptors during induced alterations in membrane potential
Mentor:Matthew Gdovin, Assistant Professor of Biology, University of Texas, San Antonio
Sudden Infant Death Syndrome (SIDS) is the spontaneous and unexpected death of an infant who is less than one year of age. Even though the incidence of SIDS has declined by more than 50% since 1990, SIDS represents the third leading cause of infant fatalities in the United States. Although risk factors associated with an increased incidence of SIDS have been described, the cause of death and documented health disparity basis of SIDS remain unexplained. Dysfunctions of brainstem regions responsible for central carbon dioxide chemoreception have been proposed as an underlying pathophysiology of SIDS. Our experiments tested the hypothesis that an inverse relationship exists between intracellular pH (pHi) regulation by the central respiratory chemoreceptors and the neuron’s membrane potential. Simultaneous recordings of both variables were done using an in vitro brainstem preparation of the bullfrog tadpole, Lithobates catesbeianus, because of its synaptic connectivity to respiratory rhythm generators, central respiratory chemoreceptors, and motor neurons. Moreover, the ratiometric fluorescent dyes used were di-8-ANEPPS, which responds to membrane potential variances, and BCECF, which responds to changes in pHi. Using electrophysiology and ratiometric fluorescence, preliminary data demonstrated: 1) we can employ flash photolysis to induce decreases in pHi within physiological limits and; 2) it is possible to record and quantify optically, pHi regulation during extracellular pH (pHe) and pHi modifications. The definitive aim was to understand if impairments in brainstem regions responsible for central carbon dioxide chemoreception are possible mechanisms of SIDS.