Tonic activation of NMDAR contributes to the resting membrane potential of SpS neurons. Current-clamp recording with a K gluconate-based, QX-314-containing pipette solution. To enhance glutamate release in the slice, extracellular K⁺ was increased to 5 mm, and Ca²⁺ was decreased to 1.2 mm. Note that the addition of 50 μm APV caused this neuron to hyperpolarize by 6 mV and its apparent input resistance, as revealed by voltage deflections during negative current pulses (20 pA, 1 s, 0.2 Hz), to increase by ∼26%.