We focused our attention on PAR2, since it has been shown to cause VH symptoms in PI-IBS rats, and we also investigated tryptase (TPSP), which is upstream of PAR2, as well as substance P (SP) and calcitonin gene-related peptide (CGRP) which are regarded as secondary neurotransmitters in colon tissues. Here, F2RL1 is linked to irritable bowel syndrome.