Figure 5.

5-HT receptor antagonists partially block raphe stimulation effects on sensory responses. A, Top, GCaMP6f signals imaged from TH+ neurons showing raphe stimulation enhancement of responses to air inhalation in control conditions and after application of the 5-HTR antagonist methysergide (200 μm). Bottom, Signals from the same ROIs showing that odorant-evoked signals are unaffected by methysergide. B, Scatter plot of inhalation-linked responses measured from individual ROIs from three preparations (2 TH+; black, red points, 1 GAD2+; blue points), showing response to air inhalation (measured from the first inhalation after the end of the stimulus train) in control versus after methysergide conditions. All ROIs show suppressed response amplitudes. Large circles show mean odorant-evoked response amplitudes, averaged across the same ROIs in each preparation, showing no effect on odorant responses. C, Example of GCaMP6f signals imaged from GAD2+ neurons showing effects of the 5-HT₂R-selective antagonist cinanserin (200 μm) on responses to air and odorant inhalation. Cinanserin reduces the effect of raphe stimulation (top traces), but also suppresses responses to air and odorant inhalation in the absence of stimulation (bottom traces, same ROIs).