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. Author manuscript; available in PMC: 2010 Nov 1.
Published in final edited form as: Trends Endocrinol Metab. 2009 Oct 1;20(9):460–468. doi: 10.1016/j.tem.2009.05.005

Figure 3.

Figure 3

Calcium signaling function of P2XRs. Activated P2XRs generate inward cationic currents in a receptor-specific manner, and the pattern of calcium signals is determined by the rate of receptor desensitization and pore dilation. Based on these two criteria, P2XRs could be divided into (i) rapidly desensitizing receptors (P2X1R and P2X3R), which generate transient calcium signals, (ii) slowly desensitizing receptors (P2X2R, P2X4R, and P2X5R), which generate prolonged calcium signals, and (iii) non-desensitizing dilating P2X7R, which generates biphasic calcium signals. Calcium influx through the pore of channels and action potential-driven Ca2+ influx through Cav channels account for P2XR-stimulated rise in [Ca2+]i. Id, desensitizing portion of current; Ir, residual current at the end of stimulation; I1, rapidly activated current; l2, slowly developing current.