A calcium-permeable cGMP-activated cation conductance in hippocampal neurons

WHOLE-cell patch clamp recordings detected a previously unidentified cGMP-activated membrane conductance in cultured rat hippocampal neurons. This conductance is nonselectively permeable for cations and is completely but reversibly blocked by external Cd²⁺. The Ca permeability of the hippocampal cGMP-activated conductance was examined in detail, indicating that the underlying ion channels display a high relative permeability for Ca²⁺. The results indicate that hippocampal neurons contain a cGMP-activated membrane conductance that has some properties similar to the cyclic nucleotide-gated channels previously shown in sensory receptor cells and retinal neurons. In hippocampal neurons this conductance similarly could mediate membrane depolarization and Ca²⁺ fluxes in response to intracellular cGMP elevation.