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. 2022 Mar 1;11:e73777. doi: 10.7554/eLife.73777

Figure 3. Colonic SCFAs promote firing of afferents via FFA3 (A).

Figure 3.

A schematic illustration of the ex vivo proximal colon preparation. The proximal colon is superfused in the recording chamber and is cannulated at both ends. Intraluminal infusion is achieved using a syringe pump (100 µl/min). A nerve branch is dissected and inserted into a suction electrode and recording is made using neurolog and Spike software. (B) A representative trace of the colonic afferent nerve signal counting individual spikes above a preset threshold (spikes/s). Introduction of C3 is highlighted. (C) The ability of C3 to promote afferent nerve activity was compared to buffer (baseline) in segments of the proximal colon taken from either wild-type C57BL/6 or hFFA2-DREADD-HA-expressing mice. C3 increased nerve firing in both preparations (**p < 0.01 and *p < 0.05, one-way analysis of variance followed by Bonferroni’s Multiple Comparison Test). (D) Similar studies were performed with 4-methoxy-3-methyl-benzoic acid (MOMBA) using tissue from either hFFA2-DREADD-HA or CRE-MINUS mice. No significant effect of MOMBA was detected (one-way analysis of variance followed by Bonferroni’s Multiple Comparison Test). (E) TUG-1907 (3 µM) was able to increase nerve activity in tissue from C57BL/6 but not in tissue taken from FFA3-KO-βGAL mice (**p < 0.01, one-way analysis of variance followed by Bonferroni’s Multiple Comparison Test). Figure 3—source data 1.

Figure 3—source data 1. Multiunit nerve activity for Figure 3.