Fig. 2
From: Gut-brain Axis and migraine headache: a comprehensive review
Mechanisms of the effects of gut bacteria in keeping normal balance of gut-brain axis via indirect signaling. CGRP, Calcitonin gene-related peptide; CRH, Corticotrophin-releasing hormone; HPA, Hypothalamic pituitary adrenal axis; LPS, lipopolysaccharides; IL, Interleukin; TNFa, Tumor necrosis factor alpha