Ontogeny of Local Sarcoplasmic Reticulum Ca2+ Signals in Cerebral Arteries: Ca2+ Sparks as Elementary Physiological Events

Ca release through ryanodine receptors (RyRs) in the sarcoplasmic reticulum is a key element of excitation-contraction coupling in muscle. In arterial smooth muscle, Ca release through RyRs activates Ca K (KCa) channels to oppose vasoconstriction. Local Ca transients ("Ca () sparks"), apparently caused by opening of clustered RyRs, have been observed in smooth and striated muscle. We explored the fundamental issue of whether RyRs generate Ca sparks to regulate arterial smooth muscle tone by examining the function of RyRs during ontogeny of arteries in the brain. In the present study, Ca sparks were measured using the fluorescent Ca indicator fluo-3 combined with laser scanning confocal microscopy. Diameter and arterial wall [Ca] measurements obtained from isolated pressurized arteries were also used in this study to provide functional insights. Neonatal arteries (