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Calcium‐activated currents in cultured neurones from rat dorsal root ganglia
Author(s) -
Currie Kevin P.M.,
Scott Roderick H.
Publication year - 1992
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1992.tb14381.x
Subject(s) - egta , biophysics , chemistry , extracellular , intracellular , channel blocker , patch clamp , membrane potential , caffeine , calcium , electrophysiology , biochemistry , medicine , endocrinology , biology , receptor , organic chemistry
1 Voltage‐activated Ca 2+ currents and caffeine (1 to 10 m m ) were used to increase intracellular Ca 2+ in rat cultured dorsal root ganglia (DRG) neurones. Elevation of intracellular Ca 2+ resulted in activation of inward currents which were attenuated by increasing the Ca 2+ buffering capacity of cells by raising the concentration of EGTA in the patch solution to 10 m m . Low and high voltage‐activated Ca 2+ currents gave rise to Cl − tail currents in cells loaded with CsCl patch solution. Outward Ca 2+ channel currents activated at very depolarized potentials (V c + 60 mV to + 100 mV) also activated Cl − tail currents, which were enhanced when extracellular Ca 2+ was elevated from 2 m m to 4 m m . 2 The Ca 2+ ‐activated Cl − tail currents were identified by estimation of tail current reversal potential by use of a double pulse protocol and by sensitivity to the Cl − channel blocker 5‐nitro 2‐(3‐phenylpropylamino) benzoic acid (NPPB) applied at a concentration of 10 μ m . 3 Cells loaded with Cs acetate patch solution and bathed in medium containing 4 m m Ca 2+ also had prolonged Ca 2+ ‐dependent tail currents, however these smaller tail currents were insensitive to NPPB. Release of Ca 2+ from intracellular stores by caffeine gave rise to sustained inward currents in cells loaded with Cs acetate. Both Ca 2+ ‐activated tail currents and caffeine‐induced inward currents recorded from cells loaded with Cs acetate were attenuated by Tris based recording media, and had reversal potentials positive to 0 mV suggesting activity of Ca 2+ ‐activated cation channels. 4 Our data may reflect (a) different degrees of association between Ca 2+ ‐activated channels with voltage‐gated Ca 2+ channels, (b) distinct relationships between channels and intracellular Ca 2+ stores and Ca 2+ homeostatic mechanisms, (c) regulation of Ca 2+ ‐activated channels by second messengers, and (d) varying channel sensitivity to Ca 2+ , in the cell body of DRG neurones.