A, original recordings and cumulative plots show the lack of effect of 50 μM AP5 on the frequency and amplitude of mEPSCs in a lamina II neuron from spinal cord slices pretreated with 5 μM SB203580 in morphine-treated rats. B, group data show a lack of effect of AP5 on the frequency and amplitude of mEPSCs in lamina II neurons in spinal cord slices pretreated with 5 μM SB203580 from morphine-treated rats (n = 10 neurons from 3 rats). C, representative current traces show the lack of effect of 50 μM AP5 on the amplitude of monosynaptic EPSCs of a lamina II neuron from spinal cord slices pretreated with SB203580 in a morphine-treated rat. D, original current traces show a lack of effect of AP5 on the PPR of evoked monosynaptic EPSCs in spinal cord slices pretreated with SB203580 in morphine-treated rats. E, summary data show the lack of effect of 50 μM AP5 on the amplitude (n = 10 neurons from 3 rats) and PPR (n = 9 neurons from 3 rats) of monosynaptic EPSCs in lamina II neurons from spinal cord slices pretreated with SB203580 in morphine-treated rats. Data are presented as means ± SEM.