Figure 3. Role of muscarinic acetylcholine receptors (mAChRs) in steady-state goblet cell-associated antigen passage (GAP) formation and mucus secretion in the small intestine (SI) and distal colon.

GAP numbers per (A) SI villus and (B) SI crypt in mice treated with vehicle or the mAChR4 antagonist tropicamide. Mucus content of the (C) SI villus and (D) SI crypt quantified as percentage of wheat germ agglutinin-positive (WGA⁺) area per villus/crypt area in mice treated with vehicle or tropicamide. (E) Representative wide-field fluorescent image of the SI of mice treated with vehicle or tropicamide following intraluminal administration of tetramethylrodamine (TRITC)-dextran (red) and WGA staining of mucus (green). (F) GAP numbers per distal colon (DC) crypt in mice treated with vehicle, pan muscarinic receptor antagonist atropine, mAChR3 antagonist 1,1-dimethyl-4-diphenylacetoxypiperidinium iodide (4-DAMP), or mAChR1 antagonist telenzepine. (G) Representative wide-field fluorescent imaging of distal colon crypts of mice treated with vehicle, atropine, 4-DAMP, or telenzepine following intraluminal administration of TRITC-dextran (red) and Ulex europaeus agglutinin 1 (UEA1) staining of mucus. (H) Mucus content of the distal colon crypt of mice treated with vehicle or 4-DAMP, quantified as percentage of UEA1⁺ area per distal colon crypt area. Data are presented as mean ± SEM. *p<0.05, **p<0.01, ***p<0.001 as compared to vehicle. n.s. = non-significant as compared to vehicle. n = 5 in panels A–D, n = 6 in panel F (telenzepine n = 5). Each data point in A–D, F, H represents the average of 25 villi or 40 crypts from one mouse. Statistical analysis was performed using an unpaired two-sided Student’s t-test in panel A–D, H. A one-way ANOVA followed by Dunnet’s post hoc test was performed in panel F.