Myotatic reflexes in sympathectomised muscle

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Abstract
Progressive changes in the proprioceptive reflex activity of skeletal muscle follow the removal of its sympathetic innerva-tion, becoming most prominent some weeks after operation. There is a critical rate of stretch at which the same amount of stretch elicits the same myotatic reflex tension in both normal and sympathectomized muscle; at rates greater than this the sympathectomized muscle attains the greater tension and vice versa. Chronic sympathectomized muscle displays low tension under constant stretch and a marked tendency to exhibit rapid clonic movements. The muscle jerk following sympa-thectomy displays a greater mechanical tension, a larger action current wave and a longer "silent period." It is concluded that in postural contraction sympathetic axones have no direct efferent influence on skeletal muscle fibres and that the progressively cumulative changes which succeed sympathectomy depend on some trophic alteration modifying the responses of proprioceptive end organs.