A mechanism of rat vibrissal movement based on actual morphology of the intrinsic muscle using three-dimensional reconstruction.

The vibrissal capsular muscle (VCM) of the rat is known to differ from the arrector pili muscle. The purpose of the present study was to characterize the rat VCM morphologically using three-dimensional reconstruction. The rat snout skin was fixed, processed with routine histological methods, sectioned serially at a thickness of 10 µm, and then stained with Masson's trichrome. The sectioned images were reconstructed three-dimensionally using 'Reconstruct' software. The findings confirmed that the VCM is a skeletal muscle attached to the vibrissal follicle such that the latter is rooted within the former. The VCM encircles the follicle almost entirely, from base to apex, and hooks around the follicle caudally. Each one of these capsular muscles is connected to two adjacent follicles in the same row. They overlap each other in the lower part, as the rostral follicular muscle that surrounds the caudal follicle. The present findings suggest that the vibrissae are able to move more freely (under voluntary control) than other general arrector pili muscles, in line with their sensory function.