GABAB receptors weakly modulate mitral cell glutamatergic transmission. A, Baclofen (25–50 μm) application causes a small and reversible reduction in the slope of fEPSPs recorded in the external plexiform layer.Bottom, Results from nine slices. Top, fEPSPs from one representative experiment. B, Baclofen causes a small and reversible reduction in mitral cell self-excitation. Mitral cells (Vm= −50 mV) were recorded in the presence of TTX (1 μm) and picrotoxin (100 μm) in Mg2+-free aCSF. Self-excitation was evoked by brief (5–25 msec) voltage steps to 0 mV.Top, Representative traces from one experiment.Bottom, Summary of results (n= 7). Self-excitation was abolished at the end of each experiment by APV, confirming that the current was mediated by NMDARs. The dashed lines represent unity.