Influence of liquid diet feeding on calcitonin gene-related peptide-like immunoreactive nerve fibers in rat temporomandibular joints during growth period

Biomechanical factors of masticatory functions are related to the development of the temporomandibular joint (TMJ) components during growth. However, the effects on nerve fibers have not been fully clarified. We investigated the influence of masticatory muscle activity on nerve fibers in the TMJ during growth by changing the consistency of diet. Twenty 3-week-old male Wistar rats were divided into two groups. The experimental group was fed a liquid diet, while the control group had a normal hard diet. Rats were sacrificed at 6-, and 9-week-old. We investigated the expression of calcitonin gene-related peptide-like immunoreactive (CGRP-LI) nerve fibers, which are most abundant in the TMJ and have a nociceptive function, using immunohistochemistry for CGRP. No significant difference in the number of CGRP-LI nerve fibers was detected in 6-week-old rats, but in 9-week-old ones the number in the experimental group was significantly greater than that in the control. We concluded that masticatory muscle activity in the TMJ closely correlates with peripheral sensory nerve fibers during growth.