Rat medial gastrocnemius is composed of the proximal and distal compartments. To diversify these subvolumes, glycogen depletion technique based on a stimulation protocol one of the two primary nerve branches to the muscle was applied. The area of compartments, number and diameter of muscle fibers in the two distinct subvolumes on five muscle levels (10, 25, 40, 75 and 90% of muscle length) were determined. It was shown that the two smallest, opposite serial sections: close to the knee (10% of muscle length) and close to the Achilles tendon (90% of muscle length) were occupied by only one compartment, i.e. proximal and distal, respectively. In the largest section (40% of muscle length), the proximal compartment constituted 27–38% of the muscle area. Maximal number of muscle fibers in the proximal compartment was 4536–6698, while in the distal one 4773–6241. The mean muscle fibers diameter in the proximal and the distal subvolumes ranged: 36.9–54.3 µm and 46.5–63.8 µm, respectively. Additionally, in electrophysiological experiments the forces evoked by common or separate stimulation of L4 and L5 ventral roots in whole muscle and in one of compartments were measured. The ratio of forces evoked at L5/L4 ventral roots stimulation amounted to 2.18 in the proximal compartment, whereas 64.67 in the distal compartment.
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