Effects of season (summer & winter) on electrical characteristics of skeletal muscle membranes of the spiny-tailed lizard, uromastix hardwickii.

ABSTRACT

This study deals with the observation of changes with temperature variations of the seasons in the muscular electrical excitability in the reptile Uromastix hardwickii. Freshly captured adult animals of both the sexes were used in all the experiments, and the gastrocnemius (skeletal) muscles were dissected out. The muscle samples were digested with digestive fluid (pepsin & Hcl), stirred, settled and supernatant was removed, till whitish fluid having clear cells obtained for patch clamp recording of ionic currents and potentials. Resting membrane potentials and action potentials of reptilian cell membranes were measured in whole cell current mode. The glass microelectrodes, with a tip diameter 2–3 μm and tip resistance 5–6 MW (when filled with intracellular solution) were used in these experiments. The present study was carried out to investigate the electrical characteristics of the skeletal muscles of this species of Uromastix, which are not studied earlier. The average mean values of resting membrane potential, action potential and its durations showed no significant changes with the change in the season, but other components of action potential including threshold potential, after-potential and its duration were found to be increased significantly (P<0.05) in summer as compared to winter. Temperature dependency of these parameters with seasonal variation, are studied for the first time in the gastrocnemius (skeletal) muscles of Uromastix hardwickii. Hence seasonal changes in the components of action potential are invariably associated with changes in environmental temperature, and may be responsible for changes in the activities and homeostasis of these animals; and possibly indicating underlying mechanism of hibernation.