ryanodine and diazo-2

The whole cell patch clamp technique was used to study the effects of changes in [Ca2+]i on the excitability of cultured dorsal root ganglion (DRG) neurones. Increases in [Ca2+]i caused membrane depolarization, altered the characteristics of evoked action potentials and activated potassium, chloride and non-selective cation conductances. Mobilization of Ca2+ from intracellular stores with caffeine (1 mM) or ryanodine (10 microM) or photorelease of Ca2+ from DM-nitrophen gave rise to depolarizations suggesting a dominant inward current under our recording conditions of low [Ca2+]i buffering capacity. The actions of [Ca2+]i could be partially reversed by intracellular flash photolysis of diazo-2 but not by diazo-3. The electrophysiological properties of some DRG neurones were not influenced by changes in [Ca2+]i and we suggest that this is because in this heterogeneous culture some neurones do not express Ca2+-activated ion channels.

Topics: Acetates; Animals; Buffers; Caffeine; Calcium; Cells, Cultured; Chelating Agents; Diazonium Compounds; Egtazic Acid; Electric Conductivity; Ethylenediamines; Ganglia, Spinal; Membrane Potentials; Neurons; Patch-Clamp Techniques; Phenoxyacetates; Phosphodiesterase Inhibitors; Photochemistry; Rats; Rats, Wistar; Ryanodine