Hypoxia Does Not Uniformly Facilitate the Release of Multiple Transmitters from the Carotid Body
Studies from diverse species have established that type I cell, the putative oxygen sensing element of the carotid body (CB), expresses a variety of conventional neurotransmitters like acetylcholine (ACh), dopamine (DA), and neuropeptides and unconventional neurotransmitters like NO and CO [for recent reviews see, (Prabhakar 2000; Kumar and Prabhakar 2002)]. An essential step in the initiation of the sensory response of the CB to hypoxia involves the release of one or more of neurotransmitters from type I cells onto apposed sensory nerve endings (Prabhakar 2000). From direct measurement of neurotransmitter release, it has been shown that hypoxia facilitates the release of both DA (Fidone et al. 1982; Bairam et al. 1996; Chen et al. 2000), and substance P (Kim et al. 2001) in the rabbit CB. On the other hand, hypoxia facilitates ACh release in the cat CB (Fitzgerald et al. 1999). However, it has not yet been determined by simultaneous monitoring of several transmitters whether hypoxia in a given species evokes the release of multiple or only a subset of transmitters in the CB.
KeywordsHPLC EDTA Dopamine Citrate Pyrolysis
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- Kumar G. K. and Prabhakar N. R. (2002) Multiple roles of neurotransmitters in the carotid body: involvement in sensory transmission and adaptation to hypoxia, in Oxygen Sensing: Responses and Adaptation to Hypoxia (Lahiri S., Prabharkar, N.R., and Semenza, G., ed. ). Marcel Dekker, New York., in press.Google Scholar