Combined effects of nitrate and caffeine on contractions of skeletal muscles

¹ Department of Rehabilitation Medicine, State University of New York, Downstate Medical Center, Brooklyn, New York

Joint action of 1 mm caffeine and NO₃^– after exposure to NO₃^– alone did not increase tension output of excised, curarized gastrocnemius muscles of healthy mice beyond NO₃^– values. In dystrophic mouse muscles, twitch tension increased further and 1.5 times as much as in 1 mm caffeine alone. In both muscles caffeine pretreatment permitted NO₃^– further to enhance twitch tension as though it were acting alone. Caffeine enhancement of tetanus tension disappeared in normal and rose further in dystrophic muscles. In both muscles jointly evoked maximal twitch tensions were the same regardless of pretreatment. Neither agent alone could duplicate jointly elicited tension increases. In excised, curarized frog sartorius muscles jointly produced twitch tensions after NO₃^– pretreatment were the sum of individual NO₃^– and caffeine enhancements. Caffeine pretreatment reduced the subsequent NO₃^– alone. These results suggest defects in NO₃^–-susceptible Ca⁺⁺ sites of dystrophic membranes, and greater sensitivity to caffeine-induced Ca⁺⁺ mobility in frog than in mouse muscles.

Key Words: nitrate-caffeine interaction • mouse skeletal muscle • frog skeletal muscle • tension output potentiation • muscular dystrophy

Submitted on September 24, 1964