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. 2016 Jun 22;36(25):6820–6835. doi: 10.1523/JNEUROSCI.3667-15.2016

Figure 6.

Figure 6.

Raphe stimulation increases basal calcium signaling in mitral/tufted cells without affecting evoked sensory responses. A, Expression of GCaMP3 in OB MT cells after injection of AAV-flex-GCaMP3 into the anterior piriform cortex of a Pcdh21-Cre mouse. Scale bar, 50 μm. Bi, Example of PCdh21+ fluorescence changes evoked by raphe stimulation during inhalation of ambient air (sniff) and in the same ROIs in the absence of inhalation (no sniff). Note that the tonic fluorescence increase is nearly identical in the presence and absence of inhalation. Bii, Mean MT cell GCaMP signal elicited by raphe stimulation during inhalation of ambient air (sniff trace not shown), averaged across seven mice, showing gradual fluorescence increase and recovery with no apparent enhancement of inhalation-linked responses, in contrast to the effects seen in GAD2+ and TH+ neurons. C, MT cell response maps elicited by odorant (top) and raphe stimulation during ambient air inhalation (bottom), with raphe stimulation eliciting a diffuse increase that was largest in the caudal OB. D, Example of PCdh21+ MT cell GCaMP signals elicited by raphe stimulus trains of increasing duration, with longer duration trains leading to slower recovery to baseline after the stimulation ceases but no emergence of inhalation-linked transients. E, MT cell responses to raphe stimulation during odorant. Traces show GCaMP signals averaged across 10 odorant-responsive ROIs (ethyl butyrate, 0.2%, s.v.) with and without raphe stimulation. Same mouse as shown in C. Raphe stimulation elicits only a small fluorescence increase in the presence of odorant, with a very small increase in the amplitude of the inhalation-linked transient. Snippets of the response just before (“pre”) and just after (“post”) the stimulus train are shown to the right. F, Scatter plot of odorant RR measured separately for 10–12 ROIs in each of four preparations (0.2–0.5%, s.v. ethyl butyrate, preparation indicated by color), showing a range of effects of raphe stimulation on odorant RR with most ROIs showing an increase.