Biphasic action of axonal GABA-A receptors on presynaptic calcium influx

J Neurophysiol. 2011 Jun;105(6):2931-6. doi: 10.1152/jn.01125.2010. Epub 2011 Apr 6.


Although ionotropic γ-aminobutyric acid A receptors (GABA(A)Rs) have long been known to exist on the axons of many different cells, their effect on axon excitability and synaptic transmission remains controversial. Here, using high-speed Ca(2+) imaging, it is shown that they induce a biphasic effect in parallel fibers of the cerebellar cortex. Multicellular measurements indicate a facilitation of action potential (AP)-evoked Ca(2+) transients, which is subsequently followed by depression. However, the receptor activation does not increase influx of Ca(2+) into individual fibers but instead, increases the probability of AP generation. These results provide a description of the effect of presynaptic GABA(A)R activation and explain why reports of the effect of their activation have been so varied.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Newborn
  • Axons / drug effects
  • Axons / metabolism*
  • Calcium / metabolism*
  • Cerebellum / cytology*
  • Electric Stimulation / methods
  • Extracellular Fluid / physiology
  • GABA Antagonists / pharmacology
  • GABA-A Receptor Agonists / pharmacology
  • Glycine / analogs & derivatives
  • In Vitro Techniques
  • Muscimol / pharmacology
  • Neurons / cytology*
  • Presynaptic Terminals / drug effects
  • Presynaptic Terminals / metabolism*
  • Pyridazines / pharmacology
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, GABA-A / metabolism*
  • Xanthenes


  • GABA Antagonists
  • GABA-A Receptor Agonists
  • Pyridazines
  • Receptors, GABA-A
  • Xanthenes
  • magnesium green
  • Muscimol
  • gabazine
  • Calcium
  • Glycine