Calcitonin gene-related peptide immunoreactive (CGRP-IR) intradental nerves in the dog

Calcitonin gene-related peptide (CGRP) is the most frequently occurring peptide in sensory neurons in the rat. Most of the Calcitonin Gene-Related Peptide Immunoreactive (CGRP-IP) nerves have been found to be Capsaicin-sensitive suggesting an involvement in certain types of pain. In the dental pulp CGRP-IR nerve fibres have been studied in the rat, guinea pig, cat, sheep, pig, cow and horse but not in the dog. Extensive sprouting of CGRP-IP intradental nerves has been demonstrated in the teeth with pulpal inflammation in rat molars. In the present investigation the occurrence and distribution of CGRP-IR intradental nerves both in the normal and the injured and inflamed teeth of the dog was studied. Immunolabelling was done by the Avidin-Biotin Complex (ABC) immunoperoxidase technique. CGRP-IR intradental nerves were demonstrated in the dog. The pattern of distribution was found to be similar to that in other animal species. However, the tip one third of the coronal pulp was sparsely innervated compared to that in the rat. Also much fewer fibres were seen to penetrate predentine and dentine, and this appears characteristic of the dog teeth. Sprouting phenomenon seen in the rat was not found in the dog teeth. It is suggested that there might be a species difference in the innervation pattern of CGRP-IR intradental nerves between the rat molar and the dog canine and incisor teeth.