Tonically active GABA A receptors: modulating gain and maintaining the tone

Trends Neurosci. 2004 May;27(5):262-9. doi: 10.1016/j.tins.2004.03.005.


GABAA receptors not only respond to the local release of GABA from presynaptic terminals, but can also mediate a persistent 'tonic current'. This reflects the activation of high-affinity GABAA receptors by ambient GABA concentrations. Tonic GABAA-receptor-mediated signalling occurs in different brain regions, shows cell-type-specific differences in magnitude and pharmacology, and changes during brain development. Some clues to the adaptive significance of this phenomenon are beginning to emerge: in cerebellar granule cells, it alters the gain of transmission of rate-coded sensory information; in the hippocampus, it acts in a cell-type-specific manner to regulate the excitability of the network. Because tonic conductances can be modulated by changes in GABA release and uptake, and by modulators of high-affinity GABAA receptors including neurosteroids, this phenomenon provides a potentially important new window onto neuronal information processing and pathological states such as epilepsy.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Action Potentials / physiology*
  • Animals
  • Brain / cytology*
  • Cells, Cultured
  • Models, Neurological
  • Nerve Net / physiology
  • Neural Inhibition / physiology
  • Neurons / classification
  • Neurons / cytology
  • Neurons / physiology*
  • Presynaptic Terminals / metabolism
  • Receptors, GABA-A / classification
  • Receptors, GABA-A / physiology*
  • gamma-Aminobutyric Acid / metabolism*


  • Receptors, GABA-A
  • gamma-Aminobutyric Acid