Effect of almitrine on upper airway muscle contraction in young and old rats

The effects of almitrine on the contractile properties of isolated geniohyoid and sternohyoid muscles were determined in physiological salt solution at 30 degrees C in young and old rats. In young rats, almitrine had no effect on twitch or tetanic tension, twitch:tetanic tension ratio, contractile kinetics, active or passive tension-length relationships or frequency-tension relationship in both muscles. Almitrine significantly increased resistance to fatigue in both muscles. In old rats, almitrine had no effect on twitch or tetanic tension, twitch:tetanic tension ratio, contractile kinetics, active or passive tension-length relationships, frequency-tension relationship or fatigue in both muscles. These results show that almitrine, in both young and old rats, has no effect on most of the contractile properties of isolated geniohyoid and sternohyoid muscles. However, almitrine increases resistance to fatigue in both muscles in young but not in old rats.