Mechanical response of lizard skeletal muscles to disuse: I. Effect of short-term tenotomization

The gastrocnemius muscles of the reptile, Uromastix hardwickii were tenotomized for seven days according to the method described earlier and their mechanical responses were recorded to study the effect of cessation of proprioceptive impulses on the functioning of these muscles. The parameters measured were isometric twitch and tetanic tensions, time dependent tension parameters and other time dependent parameters of twitch and tetanus records. The isometric twitch and tetanic tensions, their ratios and the rate of rise in twitch and tetanus along with P/ms were found significantly lesser in the tenotomized muscles. The other time dependent tension parameters, i.e. twitch contraction and tetanus half relaxation times and their ratios were however, unaffected as compared to their controls. The duration of active state on the contrary, was significantly reduced in the tenotomized muscles. The tenotomization effects observed on the mechanical parameters are discussed in terms of muscle fiber architecture and the degree/rate of cross bridge interaction in these muscles.