Abstract
All vertebrates “sense” changes in oxygen (O2) via specialized cells, called chemoreceptors, associated with the peripheral nervous system. Aquatic vertebrates are especially prone to fluctuations in environmental O2 levels. Thus it is essential for them to readily detect low O2 and make appropriate ventilatory adjustments. Teleost species, such as zebrafish, have O2 chemoreceptive neuroepithelial cells (NECs) embedded in the gill epithelium. These cells exhibit membrane depolarization and vesicular recycling upon exposure to hypoxia, and express the monoamine neurotransmitter, serotonin (5‐HT). Our research objectives are to identify gill O2 chemoreceptors in live tissue preparations and determine the role of intracellular Ca2+ in O2 sensing. We are currently employing a transgenic zebrafish line, expressing green fluorescent protein (GFP) under the control of vesicular monoamine transporter 2 (vmat2) regulatory elements, in order to identify NECs and characterize their hypoxic responses in vitro and in situ. Immunohistochemistry and confocal microscopy were used to determine the distribution and identity of GFP‐positive cells in gills. Our results show that the population of GFP‐positive cells in our transgenic line significantly overlaps with serotonergic NECs in the gill filaments. Preliminary studies using fura 2‐based imaging indicate that isolated GFP‐positive cells stimulated by hypoxia undergo an increase in intracellular Ca2+ concentration. Identification of NECs both in vitro and in situ using a vital marker will have a great impact on future work addressing the physiological properties of these cells.Support or Funding InformationThis research project is funded by Natural Sciences and Engineering Research Council of Canada (NSERC).
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