The Ryanodine receptor (RYR) is a Ca2+ channel which is sensitive to caffeine and ryanodine. RYR1 is the skeletal muscle form of the RYR, whereas RYR2 is the cardiac form, and RYR3 is the brain form. RYR1 along with the DHPR are the critical mediators of Ca2+ efflux from the sarcoplasmic reticulum to the myoplasm during excitation-contraction coupling. RYR3 is thought to play a central role in Ca2+ homeostasis in the central nervous system.