Spontaneous GABA-mediated synaptic currents in cerebellar granule cells in culture.
The whole-cell configuration of the patch clamp technique was used to characterize the electrophysiological properties of spontaneous GABA-mediated synaptic currents in cerebellar granule cells grown in a low (5 mM) potassium medium. In the presence of kynurenic acid (1 mM), to block the excitatory drive, bicuculline-sensitive synaptic events were recorded. Their amplitude distribution could be fitted by several Gaussians having the same interpeak distance. In tetrodotoxin (TTX, 1 microM) spontaneous miniature events occurred at a lower frequency. Spontaneous currents reversed polarity at 8.17 +/- 0.63 mV, a potential close to ECl; the decay phase could be fitted with a single exponential having at -60 mV a time constant of 48.7 +/- 1.5 ms. In low noise recordings, channel closing could be resolved during the decay phase of miniature events. It appeared that a single quantum of GABA opened few channels on the postsynaptic membrane.
Virginio
C
C
Biophysics Laboratory, International School for Advanced Studies (SISSA), Trieste, Italy.
Martina
M
M
Cherubini
E
E
D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D002478:Cells, Cultured; D002531:Cerebellum / Q000502:physiology*; D004594:Electrophysiology; D007736:Kynurenic Acid / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects*; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D009435:Synaptic Transmission / Q000502:physiology*; D013997:Time Factors; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
D005680:gamma-Aminobutyric Acid; D007736:Kynurenic Acid; D001640:Bicuculline