Ca2+ sparks promote myogenic tone in retinal arterioles

摘要: Background and Purpose Ca2+ imaging reveals subcellular Ca2+ sparks global waves/oscillations in vascular smooth muscle. It is well established that can relax arteries, but we have previously reported summate to generate unpressurized retinal arterioles, leading constriction. We extended these studies test the functional significance of generation myogenic tone pressurized arterioles. Experimental Approach Isolated arterioles (25–40 μm external diameter) were 70 mmHg, active signals imaged from arteriolar muscle same vessels using Fluo4 confocal laser microscopy. Key Results Tone development was associated with an increased frequency oscillations. Vasomotion observed 40% synchronization oscillations, quantifiable as cross-correlation coefficient. Inhibition ryanodine, tetracaine, cyclopiazonic acid or nimodipine, following removal extracellular Ca2+, resulted relaxation. Cyclopiazonic acid-induced dilatation decreased oscillations a sustained rise mean cytoplasmic [Ca2+] ([Ca2+]c), measured Fura2 microfluorimetry. Conclusions Implications This study provides direct evidence play excitatory role promoting tone. This contrasts generally accepted model which promote relaxation Changes vessel presence correlated more closely changes spark oscillation than [Ca2+]c, underlining importance frequency-modulated signalling