| Autor: |
Currie KP; Department of Physiology, St. George's Hospital Medical School, London., Scott RH |
| Jazyk: |
angličtina |
| Zdroj: |
British journal of pharmacology [Br J Pharmacol] 1992 Jul; Vol. 106 (3), pp. 593-602. |
| DOI: |
10.1111/j.1476-5381.1992.tb14381.x |
| Abstrakt: |
1. Voltage-activated Ca2+ currents and caffeine (1 to 10 mM) were used to increase intracellular Ca2+ in rat cultured dorsal root ganglia (DRG) neurones. Elevation of intracellular Ca2+ resulted in activation of inward currents which were attenuated by increasing the Ca2+ buffering capacity of cells by raising the concentration of EGTA in the patch solution to 10 mM. Low and high voltage-activated Ca2+ currents gave rise to Cl- tail currents in cells loaded with CsCl patch solution. Outward Ca2+ channel currents activated at very depolarized potentials (Vc + 60 mV to + 100 mV) also activated Cl- tail currents, which were enhanced when extracellular Ca2+ was elevated from 2 mM to 4 mM. 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-phenyl-propylamino) benzoic acid (NPPB) applied at a concentration of 10 microM. 3. Cells loaded with Cs acetate patch solution and bathed in medium containing 4 mM Ca2+ also had prolonged Ca(2+)-dependent tail currents, however these smaller tail currents were insensitive to NPPB. Release of Ca2+ 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 Ca2+-activated channels with voltage-gated Ca2+ channels, (b) distinct relationships between channels and intracellular Ca2" stores and Ca2+ homeostatic mechanisms, (c) regulation of Ca2+-activated channels by second messengers, and (d) varying channel sensitivity to Ca2 , in the cell body of DRG neurones. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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