An exploration of potential tonic ATP release pathways from the olfactory epithelium of mice
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In vertebrates the olfactory epithelium (OE) is the tissue responsible for conducting chemosensory stimulation. This tissue type is also exceptional in that it is the only component of the nervous system to undergo continuous regeneration in adults. Adenosine-triphosphate (ATP) is thought to be a key modulator of this process, propagating a transduction pathway resulting in mature cell development from pleuripotent cells located in the basal lamina of the OE. It has already been shown that ATP is released from the OE in response to injury or toxicity. It then binds to purinergic receptor expressed in nearby cells whose activation is thought to lead to cytoprotection and regeneration of new cells (Hegg et al., 2003). However, no mechanism has yet been identified for the delivery of ATP into the extracellular milieu under normal conditions. This study was attempted in order to identify any sources of ATP release from OE under tonic, unstressed conditions by observing the results of potential pathway inhibition and localizing proteins associated with ATP transmission through immunoreactivity. We found that a potential source, ABC transporter proteins, are present in OE and are located in the sustentacular cells. Yet, use of probenecid as an ABC transporter inhibitor did not significantly affect output of ATP from OE. The extracellular concentration of ATP was significantly affected by treatment of OE with a known blocker of the maxi-anion channel, suggesting a role for this type of transport in A TP release under normal conditions. Further research is required to fully identify the extent to which each of these pathways may contribute to intercellular signaling within mouse OE via an ATP messenger. The full elucidation of the molecular events that precipitate neuroregeneration may help to determine which factors are involved in the promotion of neural growth in all nervous tissue.