Effect of oxotremorine-M on GABAergic sIPSCs of lamina II neurons was abolished in Ca2+-free solution. A, Representative traces show GABAergic sIPSCs of one lamina II neuron during control, application of 3 μM oxotremorine-M (oxo-M) in either Ca2+-free or Krebs solution. B, Cumulative distribution plots of the inter-event interval and amplitude of sIPSCs of the same neuron in A during control and application of oxotremorine-M in either Ca2+-free or Krebs solution. C, Summary data show the effect of oxotremorine-M on sIPSCs was abolished in Ca2+-free solution but recovered in Krebs solution (n = 8). D, Group data show that repeated application of 3 μM oxotremorine-M had a reproducible effect on the frequency of sIPSCs (n = 11). Data are presented as means ± S.E.M. *, P < 0.05 compared with the pre-drug control.