GABA_B receptor activation inhibits IPSCs evoked in mitral cells by granule cell stimulation.A, Summary plot (n = 9) of the action of baclofen (25–50 μm) on IPSC amplitude. After the washout of baclofen, CGP 55845 (5 μm) caused a recovery of IPSC amplitude. Top, Traces from a representative experiment using paired-pulse stimulation (50 msec interstimulus interval). At the end of the experiment, bicuculline methiodide (+BMI; 20 μm) abolished the IPSC, confirming that it was mediated by GABA_A receptors. Thedashed line represents unity. B, Summary of results from cells in which paired-pulse stimulation was applied (n= 4, each point is the average of 6 consecutive IPSCs). Baclofen caused a change from paired-pulse depression to paired-pulse facilitation that was reversed after washout into CGP 55845. Top, Traces from one cell showing the IPSCs before (Control) and after baclofen and after the traces are scaled to the peak of the first IPSC (Scaled). The dashed line represents the average ratio during control.