Neuromodulators recruit different mechanisms to achieve their effects. (A) Time series recordings (every 20 s) of P1 and P2 amplitude responses to select neuromodulators before and after perfusion with bicuculline for assessment of effects on spontaneous and evoked inhibition. (B) Time series recording of P2/P1 ratio before and after bicuculline perfusion for assessment of inhibition on frequency-dependent transmission. Amplitudes or ratios were normalized to the average of ten traces immediately preceding neuromodulator application to enable comparison. *P < 0.05, paired t-test. 5-HT, serotonin (N = 5 slices from five mice); ACh, acetylcholine (N = 6 slices from five animals); NE, norepinephrine (N = 7 slices from four animals); min, minutes; P1, pulse 1; P2, pulse 2.