Responsiveness of the Terminal Vascular Bed in Fast and Slow Skeletal Muscles to α-Adrenergic Stimulation

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Abstract
In the light of known differences in bio-chemical, histological, and biophysical characteristics of fast and slow muscle, it was thought feasible to investigate possible differences in vascular properties. The present study has shown that vascular reactivity to α-adrenergic stimulation by both topical application of catecholamines (epinephrine and norepinephrine) and reflex activation of sympathetic nerves, is graded in both fast and slow muscles from precapillary sphincters which are the most sensitive, to small and then larger arterioles. In addition, the vessels of fast muscle are more sensitive to stimulation by those agents than are the vessels of slow muscle. The vascular bed in fast muscle is characterized by vasomotion (intermittency of flow rate and pattern) and many momentarily inactive capillaries (no moving red cells) in the resting state, whereas the flow in slow muscle capillaries is much more steady and uniform.

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