The effect of lumbar sympathectomy on fiber composition, contractility of skeletal muscle and regulation of central circulation in dogs

Publisher Website
Google Scholar
Abstract
The sympathetic activity might be of significance for fiber composition in skeletal muscle and by similar features indirectly affecting muscle contractility and regulation of circulation. Unilateral lumbar sympathectomy from L-2 and down was applied on 5 female beagle dogs. After 14 wk the gracilis muscle on both the sympathectomized and the control side was examined for its muscle fiber composition, endurance capacity and how heart rate and blood pressure responses were affected. Muscle fiber composition decreased to 28% slow twitch fibers as compared to 41% on the control side (P < 0.01). The relative cross-sectional area of the fast twitch fibers increased simultaneously from 57 (control side) to 71% (P < 0.05). Endurance performance measured as contraction time at 50% of peak tension decreased from 55-29 s (P < 0.05). On an individual bases including both control and sympathectomized muscles heart rate increased with percent fast twitch muscle fibers (P < 0.01) and a tendency was present for a similar relationship between blood pressure and fiber types (P < 0.1).