Activation of Ca(2+)-dependent K(+) channels contributes to rhythmic firing of action potentials in mouse pancreatic beta cells

J Gen Physiol. 1999 Dec;114(6):759-70. doi: 10.1085/jgp.114.6.759.

Abstract

We have applied the perforated patch whole-cell technique to beta cells within intact pancreatic islets to identify the current underlying the glucose-induced rhythmic firing of action potentials. Trains of depolarizations (to simulate glucose-induced electrical activity) resulted in the gradual (time constant: 2.3 s) development of a small (<0.8 nS) K(+) conductance. The current was dependent on Ca(2+) influx but unaffected by apamin and charybdotoxin, two blockers of Ca(2+)-activated K(+) channels, and was insensitive to tolbutamide (a blocker of ATP-regulated K(+) channels) but partially (>60%) blocked by high (10-20 mM) concentrations of tetraethylammonium. Upon cessation of electrical stimulation, the current deactivated exponentially with a time constant of 6.5 s. This is similar to the interval between two successive bursts of action potentials. We propose that this Ca(2+)-activated K(+) current plays an important role in the generation of oscillatory electrical activity in the beta cell.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP-Binding Cassette Transporters
  • Action Potentials / physiology
  • Animals
  • Electrophysiology
  • Hypoglycemic Agents / pharmacology
  • In Vitro Techniques
  • Islets of Langerhans / physiology*
  • KATP Channels
  • Large-Conductance Calcium-Activated Potassium Channels
  • Membrane Potentials / physiology
  • Mice
  • Patch-Clamp Techniques
  • Potassium Channel Blockers
  • Potassium Channels / agonists
  • Potassium Channels / metabolism
  • Potassium Channels / physiology*
  • Potassium Channels, Calcium-Activated*
  • Potassium Channels, Inwardly Rectifying
  • Tolbutamide / pharmacology

Substances

  • ATP-Binding Cassette Transporters
  • Hypoglycemic Agents
  • KATP Channels
  • Large-Conductance Calcium-Activated Potassium Channels
  • Potassium Channel Blockers
  • Potassium Channels
  • Potassium Channels, Calcium-Activated
  • Potassium Channels, Inwardly Rectifying
  • uK-ATP-1 potassium channel
  • Tolbutamide