Ca2+ channels from brain microsomal membranes reconstituted in patch-clamped bilayers.

Single Ca2+ channels from brain microsomal membranes were reconstituted in bilayers made at the tips of patch-clamp micropipettes. The single-channel conductance was defined to be 107 pS in 50 mM Ca2+. The channel activity was stimulated by nucleotides and inositol 1,4,5-trisphosphate (Ins-P3), and was inhibited by ruthenium red. Na+ added asymmetrically to the membrane bilayer induced an increase in the Ca2+-channel activity. The described characteristics of these Ca2+ channels suggest that they may be responsible for the Ca2+ transport across the membranes of the endoplasmic reticulum system triggering and modulating various neurosecretory and excitatory processes in nerve cells.