(A) Extracellular mitral cell recording configuration. An extracellular glass electrode was advanced into the AOB (magenta oval) while stimuli were applied to the VNO lumen (red oval) via a polyimide cannula. (B) Recording from a single trial stimulus pair. Top: stimulation of VSNs with 50 mM K+ Ringer's solution (“high K+”, solid black bar) induced spiking in the mitral cell. Inset: sorted spike waveforms from this trial. (C) Peristimulus time histograms in baseline (C1) and following 10 minutes of superfusion with 3 μM SR95531 (gabazine, C2). Exposure to gabazine increased the evoked activity in this cell by an average of 3.1 Hz over the 7-second integration window. Stimulus time: 5 s (solid black bar). (D) Mitral cell spontaneous activity did not significantly increase during exposure to 3 μM gabazine (p = 0.52, n = 7). (E) Mitral cell responses to VNO stimulation was significantly increased during exposure to 3 μM gabazine (p < 0.05, n = 7), indicating inhibitory activity remains present in ex vivo preparations over the 6-hour recording period.