Opening of a ligand-gated ion channel is the step at which the binding of neurotransmitter is transduced into the electrical signal by allowing ions to flow through the transmembrane channel, thereby altering the postsynaptic membrane potential. We report the kinetics for the opening of the GluR1Qflip channel, an AMPA receptor subunit of the ionotropic glutamate receptors. Using a laser-pulse photolysis technique, which permits glutamate to be liberated photolytically from -O-(a-carboxy-2-nitrobenzyl)glutamate (caged glutamate) with a time constant of ~30 µs, we show that after the binding of glutamate, the channel opens with a rate constant of (2.9 ± 0.2)×104 s-1 and closes with a rate constant of (2.1 ± 0.1)×103 s-1. The observed, shortest rise time (20-80% of the receptor current response), i.e., the fastest time by which the GluR1Qflip channel can open, is predicted to be 35 µs. This value is three times shorter than those previously reported. The minimal kinetic mechanism for the channel opening consists of binding of two glutamate molecules, with the channel-opening probability being 0.93 ± 0.1. These findings identify GluR1Qflip as one of the temporally efficient receptors to transduce the binding of chemical signals (i.e., glutamate) into an electrical impulse.