The effect of caffeine on normal and denervated gastrocnemius muscles of Uromastix hardwickii.

The effect of time and 5 mM caffeine was studied on the maximum twitch tension of the normal and 11-13 days denervated gastrocnemius muscles of Uromastix hardwickii. The maximum twitch tension was found to decrease with time and it remained about 68% of initial after 60 minutes at 20 degrees C. Five mM caffeine only produced potentiation in normal and denervated muscles while there was no contracture in either muscle. Although caffeine increased the overall contraction and relaxation times in control muscles, it was more effective on the contraction time of the denervated muscles in which the contraction time increased with time. Denervated muscles were seen to be less sensitive to caffeine as the contraction times increased with time (at about 30-40 minutes) in these muscles while in normal control muscles the contraction time increased immediately. The action of caffeine in relation to these effects is discussed.