8-Bromo-cADP-Ribose (8-Br-cADPR), a cell permeable antagonist of cADPR, has been shown to block cADPR from inducing Ca2+ release from sea-urchin-egg homogenates. cADPR has also been observed to regulate calcium release from the sarcoplasmic and endoplasmic reticulum. The antagonist displays the capacity to inhibit arrhythmogenic oscillations of intracellular Ca2+ in heart cells. Additionally, this agent has been reported to be an endogenous metabolite of β-NAD+.