The distribution and relative frequency of nerves containing immunoreactivity for substance P (SP), vasoactive intestinal polypeptide (VIP), gastrin-releasing polypeptide (GRP), calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY) and menthionine-enkephalin (MENK) were studied by immunohistochemistry in the gastrointestinal tract of the herbivorous Japanese field vole, Microtus montebelli.