[Ca2+](i) elevations detected by BK channels during Ca2+ influx and muscarine-mediated release of Ca2+ from intracellular stores in rat chromaffin cells

Murali Prakriya, Christopher R. Solaro, Christopher J. Lingle*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

50 Scopus citations

Abstract

Submembrane [Ca22+](i) changes were examined in rat chromaffin cells by monitoring the activity of an endogenous Ca2+dependent protein: the large conductance Ca2+- and voltage-activated K+ channel (also known as the BK channel). The Ca2+ and voltage dependence of BE current inactivation and conductance were calibrated first by using defined [Ca2+](i) salines. This information was used to examine submembrane [Ca2+](i) elevations arising out of Ca2+ influx and muscarine-mediated release of Ca2+ from intracellular stores. During Ca2+ influx, some BK channels are exposed to [Ca2+](i) of at least 60 μM. However, the distribution of this [Ca2+](i) elevation is highly nonuniform so that the average [Ca2+](i) detected when all BK channels are activated is only ~10 μM. Intracellular dialysis with 1 mM or higher EGTA spares only the BK channels activated by the highest [Ca2+](i) during influx, whereas dialysis with 1 mM or higher BAPTA blocks activation of all BK channels. Submembrane [Ca2+](i) elevations fall rapidly after termination of short (5 msec) Ca2+ influx steps but persist above 1 μM for several hundred milliseconds after termination of long (200 msec) influx steps. In contrast to influx, the submembrane [Ca2+](i) elevations produced by release of intracellular Ca2+ by muscarinic actetylcholine receptor (mAChR) activation are much more uniform and reach peak levels of 3-5 μM. Our results suggest that during normal action potential activity only 10-20% of BK channels in each chromaffin cell see sufficient [Ca2+](i) to be activated.

Original languageEnglish (US)
Pages (from-to)4344-4359
Number of pages16
JournalJournal of Neuroscience
Volume16
Issue number14
DOIs
StatePublished - Jul 15 1996

Keywords

  • BK channels
  • K channel inactivation
  • calcium
  • calcium channels
  • calcium stores
  • catecholamine secretion
  • chromaffin cells

ASJC Scopus subject areas

  • Neuroscience(all)

Fingerprint

Dive into the research topics of '[Ca<sup>2+</sup>](i) elevations detected by BK channels during Ca<sup>2+</sup> influx and muscarine-mediated release of Ca<sup>2+</sup> from intracellular stores in rat chromaffin cells'. Together they form a unique fingerprint.

Cite this