Force-Velocity Relationship of Tetanus Toxin Treated Skeletal Muscle.

Abstract

Investigations of the force-velocity relationship of muscles actively shortened by tetanus toxin injection were carried out on the gastrocnemii of 13 male albino rats. An 11m wound clip with attached nylon monofilament was fastened to the free tendinous end. The mono-filament was connected to an isotonic myograph employing an electro-mechanioal transducer. Plots of (Po-P)/v against P were used to calculate the constants a and b of Hill''s equation. No statistically significant difference between toxin treated and control muscles can be demonstrated with regard to the velocity constants b. (Control 2.94 + 0.18 cm/second; Exp. 2.50 + 0.19 cm/second P = < 0.02). There is a clear cut, significant difference between the 2 "extra" heats of shortening as evidenced by the constants a (Control 246.5 + 8.5 g weight; Exp. 1530 + 11.0 g weight P = < 0.001). An attempt was made to interpret this change in terms of other reported mechanical and chemical changes.