ATP-gated purinergic receptors (P2XRs) are a family of cation-permeable channels that conduct Ca(2+) and facilitate voltage-sensitive Ca(2+) entry in excitable cells. To study Ca(2+) signaling by P2XRs and its dependence on voltage-sensitive Ca(2+) influx, we expressed eight cloned P2XR subtypes individually in gonadotropin-releasing hormone-secreting neurons. In all cases, ATP evoked an inward current and a rise in Ca(2+). P2XR subtypes differed in the peak amplitude of Ca(2+) response independently of the level of receptor expression, with the following order: P2X(1)R < P2X(3)R < P2X(4)R < P2X(2b)R < P2X(2a)R < P2X(7)R. During prolonged agonist stimulation, Ca(2+) signals desensitized with different rates: P2X(3)R > P2X(1)R > P2X(2b)R > P2X(4)R >> P2X(2a)R >> P2X(7)R. The pattern of Ca(2+) response for each P2XR subtype was highly comparable with that of the depolarizing current, but the activation and desensitization rates were faster for the current than for Ca(2+). The P2X(1)R, P2X(3)R, and P2X(4)R-derived Ca(2+) signals were predominantly dependent on activation of voltage-sensitive Ca(2+) influx, both voltage-sensitive and -insensitive Ca(2+) entry pathways equally contributed to Ca(2+) responses in P2X(2a)R- and P2X(2b)R-expressing cells, and P2X(7)R operated as a nonselective pore capable of conducting larger amounts of Ca(2+) independently on the status of voltage-gated Ca(2+) channels. Thus, Ca(2+) signaling by homomeric P2XRs expressed in an excitable cell is subtype-specific, which provides an effective mechanism for generating variable Ca(2+) patterns in response to a common agonist.