Key Points
- To examine the mechanisms by which neurokinin A and L-type Ca2+ currents stimulate Ca2+-activated Cl- currents in airway smooth muscle cells.
- Recorded membrane currents in isolated guinea-pig tracheal myocytes using whole-cell patch-clamp electrophysiology with a Cs+ internal solution.
- Assessed current responses under pharmacological modulation using neurokinin A, caffeine, ryanodine, heparin, inositol 1,4,5-trisphosphate (IP3), Bay K 8644, nifedipine, and DIDS across varying extracellular and intracellular ion concentrations.
- Neurokinin A (1 µM) and caffeine (10 mM) transiently evoked Ca2+-activated Cl- currents that were abolished in Ca2+-free solution upon repeated exposure; ryanodine abolished responses to both agents, whereas heparin selectively blocked neurokinin A.
- Depolarizing pulses activated L-type Ca2+ currents and inward tail currents that were potentiated by Bay K 8644, blocked by Cd2+ or nifedipine, abolished by external Ca2+ removal or internal EGTA, and exhibited Cl--dependent reversal potentials sensitive to DIDS.
- Application of neurokinin A or caffeine markedly suppressed subsequent Cl- currents activated by L-type Ca2+ current, indicating that sarcoplasmic reticulum Ca2+ depletion attenuates Ca2+-induced Ca2+ release.
Structured PICO
PPopulationGuinea-pig tracheal myocytes
IInterventionNeurokinin A (1 mu M) and caffeine (10-30 mM)
OOutcomeActivation of Ca(2+)-activated Cl- currents (I[Cl(Ca)])surrogate
Neurokinin A and caffeine induce Ca2+-activated Cl- currents in guinea-pig tracheal myocytes via sarcoplasmic reticulum Ca2+ release.