SLC6A4 and irritable bowel syndrome: Post-infective IBS, a subtype of IBS-D with very similar clinical features,20 has been shown to be associated with increased 5HT-containing enteroendocrine cells,21–23 and also increased postprandial 5-HT release.24 Further studies have also shown reduced mRNA for SERT in IBS-D duodenal25 and colonic biopsies23, 25which, in keeping with animal studies of post inflammatory bowel dysfunction,26 was correlated with mucosal immune response.