Effect of thyrotoxicosis on skeletal muscle proprioceptor activity

The effect of prolonged administration of thyroid hormones on the discharges from muscle spindles of the cat soleus was investigated. In animals with thyrotoxicosis the response of the primary spindle endings to a constantly acting and to a sudden rapid stretching increased considerably in both the dynamic and the static phase. The discharge frequency of the secondary endings remained substantially unchanged. It is postulated that the observed changes in activity of the primary endings are connected with disturbances of metabolism in the muscle and also with its atrophy.Group for Evolution of Motor Activity, Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Laboratory of Pathological Physiology, Institute of Experimental Endocrinology and Hormone Chemistry, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR N. A. Yudaev.) Translated from Byulleten' Éxperimental'noi Biologii i Meditsiny, Vol. 82, No. 10, pp. 1187–1189, October, 1976.