FIGURE 5.

The effect of butyrate at fixed levels of high and low distention on CMCs. (A) Spatiotemporal maps showing the effects of increasing butyrate concentrations on colonic motor activity under low distention. Administering 1 mM of luminal butyrate caused proximal rhythmic contractions to extend into pan-colonic CMCs, specifically FPCs. LDCs were formed at 10 mM of butyrate but disappeared upon continued increases in butyrate concentration to 30 mM or 100 mM. (B) Spatiotemporal maps showing the effects of increasing butyrate concentrations on colonic motor activity under high distention. Administering 10 mM of butyrate increased CMC frequency on average. Further increases in CMC frequencies were inconsistent in response to 30–100 mM butyrate. (C) Frequency of CMCs in response to varying concentrations of butyrate in high and low distention. Butyrate (1 mM) significantly increases CMC frequency in instances of low intraluminal pressure and activity, as simulated by low distention (0 cmH₂O of outflow pressure) (N = 10, P < 0.001). Increasing the concentration of butyrate to 10 mM, 30 mM or 100 mM did not further augment CMC frequency. Butyrate has a negligible effect on CMC frequency in instances of high intraluminal pressure and baseline motor activity, as simulated by high distention (3 cmH₂O outflow pressure) (N = 7). P values were determined by a one-way ANOVA and Tukey’s post hoc test.