It is estimated that from 1 million of adult people in the western hemisphere, 20,000 present skeletic muscle abnormalities from abusive alcohol consumption. In this case a progressive muscle weakness sets in specially in the type II fibers of the thigh, shoulder and hip muscles. In the masticatory muscles the alcohol effects are unknown. This research aimed to evaluate possible type II myofibers alterations in the digastricus muscle in order to compare with the trunk muscle. Muscle fragments from digastricus and abdominal rectus muscles of 5 animals were harvested per grouping: Control (C), Alcoholic (A) and Isocaloric (I) groups. The fragments were submitted to the myosin ATPase (acid and alkaline pre incubation) and NADH-TR reactions. The fibers were classified into FG (fast-twitch-glycolitic) FOG (fast-oxidative-glycolitic) and SO (slow-oxidative). The results showed significative difference in the FG and FOG areas of the digastricus muscle among the studied groups and only in the FG fibers in the rectus abdominalis muscle. It was also observed a significative difference in the FG and FOG fibers frequency in the abdominal rectus muscle. Based in these results we conclude that the alcohol produces an atrophy in the masticatory fast fibers (FG and FOG fibers) similar to the trunk muscle.

KEY WORDS: type of fibers; masticatory muscle; digastricus muscle; alcoholism; rats