HTR3A and irritable bowel syndrome: The inhibitory effect of capsaicin is consistent with its clinical use in topical creams, which treat pain by desensitising nociceptors.40 By contrast, the pathophysiological implications of desensitising responses to 5-HT and histamine is unclear given the clinical efficacy of 5-HT3 antagonists and histamine H1-receptor antagonists in IBS, and may be a feature of this experimental system.41, 42