Quantitative histochemical studies on the cat infrahyoid muscles.

The intrinsic laryngeal muscles have been reported to be composed of muscle fibers that have unusual physiologic, morphologic, and biochemical characteristics, and it has been suggested that the relatively unique differentiation of these muscle fibers is the result of their specific activity patterns. Because the infrahyoid muscles are recruited for some of the same laryngeal functions, it was of interest to determine if they also included unusual fiber types. In order to examine this possibility, microdensitometry was carried out on type I, type IIA, and type IIB fibers in the cat sternohyoid, sternothyroid, and thyrohyoid muscles using histochemical techniques for a variety of enzymatic markers of oxidative and glycolytic capacity and for fiber size. It was found that the infrahyoid muscles were composed of muscle fibers having enzyme profiles generally similar to those of fiber types in the limb muscles.