Hysteresis Properties of EMG Activity of the Shoulder Belt and Shoulder Muscles at the Development of Isometric Efforts by the Human Arm

• Published in: Neurophysiology (New York) Vol. 47; no. 1; pp. 61 - 70
• Main Authors: Sobolev, V. I., Trush, V. V., Litvyak, K. A., Morozova, I. N.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.02.2015; Springer; Springer Nature B.V
• Subjects: Adrenal glands; Biomedical and Life Sciences; Biomedicine; Hyperthyroidism; Muscular system; Neurobiology; Neurosciences; Rodents; Shoulder; thyroxine; hyperthyroidism; hydrocortisone; hypercorticoidism; neuromuscular transmission; skeletal muscle; M response
• ISSN: 0090-2977; 1573-9007
• DOI: 10.1007/s11062-015-9498-x

In experiments on rats, we studied the effects of experimental hyperthyroidism (subcutaneous injections of L-thyroxine, 50 μg/kg·day during 7 days) and hypercorticoidism (daily i.p. injections of hydrocortisone, 3 mg/kg·day during 30 days) on parameters of the М responses of the m. tibialis anterior after stimulation of the n. peroneus by single stimuli and their series with the instant frequency increasing linearly from 4 to 74 sec −1 . In hypercorticoidism, the latency of single М responses was, on average, 30% longer, while the amplitude was 29% lower than those in the control. Multicomponent М potentials were observed in this group more frequently (in 37.5% of the cases); the duration of these responses demonstrated no significant changes. Hyperthyroidism caused shortening of the latency of the М responses (by 15%) and a decrease in their duration (by 25%). The mean amplitude of the responses exceeded the control by 70%; significant modifications of their shape were not observed. Experimental hyperthyroidism and hypercorticoidism were accompanied by a more expressed decrease, as compared with the control, in the amplitude with increase in the frequency of stimulation of the nerve and decreased stability of generation of the responses. The frequency level at which the inverse dependence between the М response amplitude and stimulation frequency began to be clearly pronounced decreased in animals with the modified hormonal status. Probable reasons for peculiarities of the frequency dependence of the parameters of the М responses in hyperthyroidism and hypercorticoidism are discussed.