Inositol 1,4,5-trisphosphate receptors (IP3R) are ubiquitous intracellular Ca2+ channels. They are regulated by IP3 and Ca2+ and can thereby both initiate local Ca2+ release events and regeneratively propagate Ca2+ signals evoked by receptors that stimulate IP3 formation. Local signaling by small numbers of IP3R underpins the utility of IP3-evoked Ca2+ signals as a ubiquitous signaling pathway. The physiological impact of Ca2+ release by very small numbers of IP3R underscores the necessity to understand the behavior of IP3R at the single-channel level. In addition, and in common with analyses of every other ion channel, single-channel analyses have the potential to define the steps linking IP3 binding to channel opening. Patch-clamp recording, by resolving the openings and closings of single channels with exquisite temporal resolution, is the most powerful technique for analysis of single-channel events. It has contributed enormously to the understanding of gating and desensitization/inactivation of numerous ion channels. However, most IP3R reside within intracellular membranes, where they are inaccessible to conventional patch-clamp recording methods. Here, we describe the application of nuclear patch-clamp methods to single-channel analyses of native and recombinant IP3R. © 2010 Elsevier Inc.
