Potential Oxygen Sensing Pathways in the Zebrafish Gill

Regulation of arterial partial pressure of oxygen (Po2) during periods of hypoxia ensures adequate delivery of O2 to systemic tissues. Peripheral O2 chemoreceptors in mammals, such as carotid body glomus cells and neuroepithelial bodies of the lung, respond to hypoxia with a reduction of K+ current (López-Barneo et al. 1988; Youngson et al. 1993; see also Thompson et al. 1997). This cellular response is thought to initiate hyperventilation and other physiological adaptations to hypoxia through Ca2+-dependent neurosecretion and activation of post-synaptic pathways (González et al. 1994; López-Barneo et al. 2001). In water-breathing vertebrates, such as teleost fish, hypoxia induces hyperventilation, bradycardia and an increase in gill vascular resistance, and these responses arise principally from peripheral O2 chemoreceptors (Burleson et al., 1992). However, O2-sensitive cells mediating these responses have not been identified.