Effects of cutaneous afferent input on fatigue-induced changes in fusimotor activity of decerebrate cats

• Published in: Neuroscience Vol. 79; no. 3; pp. 935 - 942
• Main Authors: LJUBISAVLJEVIC, M, VUKCEVIC, I. S, RADOVANOVIC, S, MILANOVIC, S, ANASTASIJEVIC, R
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.08.1997; Elsevier
• Subjects: Afferent Pathways - physiology; Animals; Biological and medical sciences; Cats; cutaneous afferents; Decerebrate State; Fundamental and applied biological sciences. Psychology; fusimotor neurons; MEDICIN; MEDICINE; Motor Activity - physiology; Motor Neurons, Gamma - physiology; muscle fatigue; Muscle Fatigue - physiology; Striated muscle. Tendons; Vertebrates: osteoarticular system, musculoskeletal system; LGS, lateral gastrocnemius and soleus muscles; MG, medial gastrocnemius muscle; cutaneous afferents; muscle fatigue; fusimotor neurons; Motor nerve fiber γ; Fissipedia; Carnivora; Vertebrata; Mammalia; Cat; Afferent projection; Fatigue; Skin; Striated muscle
• ISSN: 0306-4522; 1873-7544; 1873-7544
• DOI: 10.1016/S0306-4522(97)00039-0

Interaction of cutaneous and small-diameter, primarily fatigue-induced, muscle afferent inputs on fusimotor neurons has been studied in decerebrate cats. Spike discharges of fusimotor neurons to medial gastrocnemius were recorded from filaments dissected free from this muscle nerve. Non-noxious mechanical stimuli (10 Hz, 2 mm vibration) were applied to the skin area on the lateral side of the heel, innervated by sural nerve, during long-lasting (250 s) fatiguing contraction of lateral gastrocnemius and soleus muscles, elicited by electrical stimulation (40 Hz, 1.3×motor threshold) of the muscle nerves. In 15 units (58%) the pattern of responses to muscle contraction and/or fatigue (initial transient, and late long-lasting increase in firing rate, respectively) was preserved in the presence of skin vibration which, by itself, provoked either a slight increase or no changes in fusimotor discharge rate. Pattern of the response to skin vibration prevailed in the presence of muscle contraction and fatigue only if the vibration by itself induced marked increase in fusimotor discharge rate (three units). In the remaining eight units the responses to both stimuli applied simultaneously were dissimilar in pattern to the response to either stimulus applied alone: the initial, tension-related, increase in firing rate was prolonged, while the late, fatigue-induced one was attenuated and its post-contraction part almost abolished. Possible mechanisms and functional role of interaction between cutaneous and muscle afferent inflows are discussed.