GABA-activated Single-channel and Tonic Currents in Rat Brain Slices

The GABA(A) channels are present in all neurons and are located both at synapses and outside of synapses where they generate phasic and tonic currents, respectively (4,5,6,7) The GABA(A) channel is a pentameric GABA-gated chloride channel. The channel subunits are grouped into 8 families (α1-6, β1-3, γ1-3, δ, ε, θ, π and ρ). Two alphas, two betas and one 3(rd) subunit form the functional channel (8). By combining studies of sub-type specific GABA-activated single-channel molecules with studies including all populations of GABA(A) channels in the neuron it becomes possible to understand the basic mechanism of neuronal inhibition and how it is modulated by pharmacological agents. We use the patch-clamp technique (9,10) to study the functional properties of the GABA(A) channels in alive neurons in hippocampal brain slices and record the single-channel and whole-cell currents. We further examine how the channels are affected by different GABA concentrations, other drugs and intra and extracellular factors. For detailed theoretical and practical description of the patch-clamp method please see The Single-Channel Recordings edited by B Sakman and E Neher (10).