Serotonin receptor 2B induces visceral hyperalgesia in rat model and patients with diarrhea-predominant irritable bowel syndrome

Figure 1 Irritable bowel syndrome with diarrhea patients presented increased serotonin receptor 2B and transient receptor potential vanilloid type 1 protein levels. A: Expression of the serotonin receptor 2B (5-HT_2B) receptor protein in colonic biopsies of patients with irritable bowel syndrome with diarrhea (IBS-D) (n = 18), patients with irritable bowel syndrome with constipation (n = 10), and control subjects (n = 15); B: Correlation between the severity of abdominal pain and the 5-HT_2B receptor level in patients with IBS-D (Spearman correlation coefficient = 0.71, P = 0.001); C: Correlation between the frequency of abdominal pain and the 5-HT_2B receptor level in patients with IBS-D (Spearman correlation, r = 0.68; P = 0.001); D: Representative photomicrographs showing positive 5-HT_2B receptor and transient receptor potential vanilloid type 1 (TRPV1) immunoreactivity in two serial sections of biopsy tissues from healthy controls and IBS-D patients. The magnification was 20 ×; E: Double-label immunofluorescence analysis of the 5-HT_2B receptor (green) and TRPV1 (red) in the colonic mucosa of healthy controls and IBS-D patients. Merged image showing colocalization (yellow) of the 5-HT_2B receptor and TRPV1 immunoreactivity. Magnification 20 ×. ^aP < 0.05. IBS-C: Irritable bowel syndrome with constipation; IBS-D: Irritable bowel syndrome with diarrhea; 5-HT_2B: Serotonin receptor 2B; HC: Healthy controls; TRPV1: Transient receptor potential vanilloid type 1.