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A. Akopian, T. Szikra, M. Cristofellini, D. Krizaj; The Actin Cytoskeleton Regulates Different Ca2+ Sources in Salamander Retinal Neurons . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2266.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To investigated involvement of actin filaments (F–actin) in regulation of intracellular [Ca2+] changes originated by influx through: 1) voltage–gated channels, 2) through glutamate receptor–activated channels, and 3) by release from internal stores. Methods: Whole–cell patch clamp technique was used to record Ca currents from ganglion cells in retinal slice preparation, calcium imaging to measure changes in intracellular Ca in isolated neurons, and immunocytochemistry was performed to evaluate changes in the F–actin organization Results: In retinal slices intense fluorescent–phalloidin staining was observed in photoreceptors, OPL, IPL and ganglion cell layers. Fluorescence intensity was reduced in the presence of F–actin disrupter, latrunculin. Depolymerization of the actin cytoskeleton by latrunculin or cytochalasin resulted in a reduction of glutamate–induced Ca2+ accumulation by 53±7% in isolated retinal neurons. By itself, the F–actin stabilizer jasplakinolide had no significant effect on glutamate–induced Ca signal. In the presence of jasplakinolide, however, the inhibitory effect of latrunculin was blocked, indicating that reduction in glutamate–induced Ca2+ influx was associated with disruption of F–actin. We also show that latrunculin A reduced caffeine–induced Ca2+ accumulation mediated through release from internal stores. In whole–cell patch clamp experiments carried out on ganglion cells in the retinal slice preparation, disruption of F–actin by latrunculin resulted in a reduction of L–type Ca current by 55±4%. The inhibitory effect of latrunculin was attenuated by co–application of F–actin stabilizer phalloidin, into the patch pipette solution. Conclusions: These data indicate that in salamander retinal neurons the actin cytoskeleton regulates external, as well as internal Ca2+ sources responsible for elevation of intracellular [Ca2+].
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