| Autor: |
Kreitzer MA; Department of Biology, Indiana Wesleyan University, Marion, Indiana, United States., Vredeveld M; Department of Biology, Indiana Wesleyan University, Marion, Indiana, United States., Tinner K; Department of Biology, Indiana Wesleyan University, Marion, Indiana, United States., Powell AM; Department of Biology, Indiana Wesleyan University, Marion, Indiana, United States., Schantz AW; Department of Biology, Indiana Wesleyan University, Marion, Indiana, United States., Leininger R; Department of Biology, Indiana Wesleyan University, Marion, Indiana, United States., Merillat R; Department of Biology, Indiana Wesleyan University, Marion, Indiana, United States., Gongwer MW; Department of Biology, Indiana Wesleyan University, Marion, Indiana, United States., Tchernookova BK; Department of Biological Sciences, University of Illinois at Chicago, Chicago, Illinois, United States., Malchow RP; Department of Biological Sciences, University of Illinois at Chicago, Chicago, Illinois, United States.; Department of Psychology, College of the Holy Cross, Worcester, Massachusetts, United States. |
| Abstrakt: |
Previous work has shown that activation of tiger salamander retinal radial glial cells by extracellular ATP induces a pronounced extracellular acidification, which has been proposed to be a potent modulator of neurotransmitter release. This study demonstrates that low micromolar concentrations of extracellular ATP similarly induce significant H + effluxes from Müller cells isolated from the axolotl retina. Müller cells were enzymatically isolated from axolotl retina and H + fluxes were measured from individual cells using self-referencing H + -selective microelectrodes. The increased H + efflux from axolotl Müller cells induced by extracellular ATP required activation of metabotropic purinergic receptors and was dependent upon calcium released from internal stores. We further found that the ATP-evoked increase in H + efflux from Müller cells of both tiger salamander and axolotl were sensitive to pharmacological agents known to interrupt calmodulin and protein kinase C (PKC) activity: chlorpromazine (CLP), trifluoperazine (TFP), and W-7 (all calmodulin inhibitors) and chelerythrine, a PKC inhibitor, all attenuated ATP-elicited increases in H + efflux. ATP-initiated H + fluxes of axolotl Müller cells were also significantly reduced by amiloride, suggesting a significant contribution by sodium-hydrogen exchangers (NHEs). In addition, α-cyano-4-hydroxycinnamate (4-cin), a monocarboxylate transport (MCT) inhibitor, also reduced the ATP-induced increase in H + efflux in both axolotl and tiger salamander Müller cells, and when combined with amiloride, abolished ATP-evoked increase in H + efflux. These data suggest that axolotl Müller cells are likely to be an excellent model system to understand the cell-signaling pathways regulating H + release from glia and the role this may play in modulating neuronal signaling. NEW & NOTEWORTHY Glial cells are a key structural part of the tripartite synapse and have been suggested to regulate synaptic transmission, but the regulatory mechanisms remain unclear. We show that extracellular ATP, a potent glial cell activator, induces H + efflux from axolotl retinal Müller (glial) cells through a calcium-dependent pathway that is likely to involve calmodulin, PKC, Na + /H + exchange, and monocarboxylate transport, and suggest that such H + release may play a key role in modulating neuronal transmission. |
