Cellular Expression of Neurokinin 1 Receptor in the Rat Duodenal Villi

The cellular expression of neurokinin 1 (NK1) receptor in the rat duodenal villi was studied at the levels of protein and mRNA by use of immunohistochemistry and in situ hybridization. Transmission electron microcopy was also performed to investigate the functional significance of the cells expressing NK1 receptor. Both the NK1 receptor-immunoreactivity and hybridization signals for its mRNA were localized in the fibroblast-like cells beneath the villous epithelium, indicating that NK1 receptor is produced and allocated in the cells. These cells connected with each other by their slender processes to form a well-developed network, which is probably provided with a contractile potential by the cellular characteristics including an abundance of cytoplasmic myofilaments and gap junctions between the processes, throughout the lamina propria of the villi. They were intimately associated with blood vessels and nerve fibers containing substance P. The present findings suggest that the contractile network of the fibroblast-like cells may regulate the blood flow of the vascular network in the villi by interaction between substance P released from the nerve terminals and its receptor on the cells.