Functional properties of GABAA receptors of AII amacrine cells of the rat retina

Amacrine cells are a highly diverse group of inhibitory retinal interneurons that sculpt the responses bipolar cells, ganglion and other amacrine cells. They integrate excitatory inputs from but for most little is known about specificity functional properties their inputs. Here, we have investigated GABA A receptors AII amacrine, critical neuron in rod pathway microcircuit, using patch-clamp recording rat slices. Puffer application evoked robust responses, but, surprisingly, spontaneous receptor-mediated postsynaptic currents were not observed, neither under control conditions nor following high-K + solution to facilitate release. To investigate biophysical pharmacological AIIs, therefore used nucleated patches fast system. Both brief long pulses (3 mM) with slow, multi-exponential decay kinetics. The average weighted time constant (τ w ) deactivation was ~163 ms. Desensitization even slower, τ ~330 Non-stationary noise analysis patch directly observed channel gating yielded single-channel conductance ~23 pS. Pharmacological investigation suggested presence α2 and/or α3 subunits, as well γ2 subunit. Such subunit combinations typical slow If synaptic amacrines similar properties, desensitization kinetics will temporal summation GABAergic inputs, allowing effective integration occur relatively low frequencies