CO2 Signaling in Chemosensory Neuroepithelial Cells of the Zebrafish Gill Filaments: Role of Intracellular Ca2+ and pH
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Adult zebrafish, Danio rerio, exhibit hyperventilatory responses to absolute environmental CO2 levels as low as 1.0 mmHg. The ability of zebrafish to detect and respond to low ambient CO2 appears to be mediated by chemosensory neuroepithelial cells (NECs) of the gill filaments. Recent electrophysiological characterization of this response revealed that the partial pressure-dependent depolarization of NECs in response to a hypercapnic stimulus is dependent on the rate of acidification associated with the hydration of CO2 and the inhibition of background K+ channels. In order to further elucidate the signaling pathway underlying CO2 chemotransduction in NECs, we used microfluorimetric techniques to study intracellular changes in pH (pHi) and calcium ([Ca2+]i). Using the ratiometric indicators BCECF-AM and fura-2-AM, we found that a hypercapnic stimulus evoked a decrease in pHi and an increase in [Ca2+]i.
KeywordsNeuroepithelial cells Hypercapnia pH Calcium Zebrafish
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