Figure 4. PV cell activity is strongly enhanced by increases in respiration rate.

(A) Top: in vivo imaging configuration with mouse on a circular treadmill. Bottom: example traces of simultaneously recorded respiration and running speed. Spontaneous running is accompanied by an increase in respiration frequency. (B) Running-related increases in respiration rate are associated with uniform increases in PV cell activity, while mitral and granule cell activity is variably modulated by changes in respiration. (B₁) Top: respiration rate during a 55 sec imaging session. Bottom, simultaneously imaged activity of ten PV cells. Cells are sorted in descending order based on correlation coefficient values between the cell activity and respiration frequency. All PV cells show increases in fluorescence during periods of high frequency respiration. (B₂) Granule cells (n = 64 cells) and (B₃) mitral cells (n = 80 cells) show more variable responses to changes in respiration frequency. (C) Normalized fluorescence intensities of individual cells shown in (B) binned with respect to respiration frequency. Fluorescence intensities are normalized to values when respiration frequency was 1–3 Hz. (C₁) Activity in PV cells increases linearly with elevations in respiration frequency. Red line: average. Gray lines: individual cells. (C₂)Mi tral and (C₃) granule cell activity show both increases and decreases in fluorescence with elevations in respiration rate. (C₄) Plugging the ipsilateral nostril blocks the respiration-modulation of PV cell activity. Error bars represent SEM. (D) Summary data of the correlations between respiration frequency and normalized fluorescence intensity (slopes of the regression lines) shown as box plots where whiskers represent most extreme values within 1.5 × I.Q.R. and outliers shown in red crosses. (PV cells: 4 mice, 38 cells; granule cells: 4 mice, 329 cells; mitral cells: 5 mice, 201 cells; PV cells with plug: 3 mice, 36 cells).