Immortalized GnRH neurons express large-conductance calcium-activated potassium channels

Neuroendocrinology. 1996 Feb;63(2):101-11. doi: 10.1159/000126946.


The expression and function of large-conductance Ca2+ -activated K+ (BK) channels in the GT1-7 line of immortalized gonadotropin-releasing hormone (GnRH) neurons was investigated. Ionic currents were recorded using the patch-clamp technique, cytoplasmic free Ca2+ concentration ([Ca2+]i) was monitored using the fluorescent indicator, fura-2, and GnRH secretion was measured by radioimmunoassay. In cell-attached and inside-out patch-clamp recordings, K+ channels with a single-channel conductance of approximately 200 pS were detected. Depolarizing the patch increased the unitary current size and the open probability. In perforated-patch recordings, depolarizing pulses (50 ms) to potentials of -10 to +60 mV from a holding potential of -90 mV elicited outward current with early transient and sustained components. The transient current peaked 2-10 ms after the beginning of each pulse and increased in a voltage-dependent manner. This current was: (1) unaffected by the small-conductance Ca2+ -activated K+ channel blocker, apamin (100 nM); (2) reduced by the BK channel blocker, charybdotoxin (5 nM); (3) abolished by the Ca2+ channel blocker, CdCl2 (25 mu M), and (4) prolonged by the endoplasmic reticulum Ca2+ -ATPase inhibitor, thapsigargin (1 mu M). Based on the single-channel and whole-cell conductances, the number of channels per patch, the patch area, and the surface area of the cell, each GT1-7 cell contains 30-60 BK channels. The functional role of BK channels in GT1-7 cells was evaluated by measuring the effect of charybdotoxin (100 nM) on basal [Ca2+]i and GnRH secretion, as well as on the [Ca2+]i and GnRH secretory responses to gamma-aminobutyric acid (GABA, 100 mu M), an excitatory neurotransmitter in this system. Charybdotoxin had no effect on basal [Ca2+]i or GnRH secretion, or on the GABA-evoked [Ca2+]i and GnRH secretory responses. These results indicate that GT1-7 cells express BK channels; however, the physiological role of BK channels in GT1-7 cells remains elusive.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Calcium / physiology*
  • Calcium Channel Blockers / pharmacology
  • Calcium-Transporting ATPases / antagonists & inhibitors
  • Cell Line
  • Enzyme Inhibitors / pharmacology
  • Gonadotropin-Releasing Hormone / metabolism*
  • Membrane Potentials / drug effects
  • Membrane Potentials / physiology
  • Mice
  • Neurons / drug effects
  • Neurons / metabolism*
  • Patch-Clamp Techniques
  • Potassium Channels / drug effects
  • Potassium Channels / metabolism*


  • Calcium Channel Blockers
  • Enzyme Inhibitors
  • Potassium Channels
  • Gonadotropin-Releasing Hormone
  • Calcium-Transporting ATPases
  • Calcium