Histochemical evidence for strictly ipsilateral innervation of maxillary canine teeth in cats

Abstract

Substantial efforts by various investigators have not shown conclusively that there is a peripheral crossed innervation of feline maxillary canine teeth. In addition, the number and location of afferent cell bodies innervating these teeth has not been adequately determined. Horseradish peroxidase (HRP) was used as a retrograde neuronal marker of the afferent fibers innervating the maxillary canine teeth in 11 cats. Cavity preparations were made in the ipsilateral canine tooth and then HRP was deposited in the cavity preparation. After survival periods of 18 to 72 h, the anesthetized animals were perfused and both the ipsilateral and contralateral ganglia were processed histochemically for the localization of the HRP reaction product. Both ganglia were studied for labeled cell bodies and their locus within the ganglia. All labeled cell bodies were in the maxillary division of the ipsilateral trigeminal ganglion. The greatest number of labeled cell bodies, in excess of 200, occurred 18 h after injection of the HRP, and was higher than reported in previous studies. The results from this study clearly indicate that the primary afferent innervation of the maxillary canine teeth in the cat is strictly ipsilateral, which casts doubt on the previous claims of a crossed or “transmedian” innervation of the maxillary canine teeth in that species.