beta-Adrenergic dilator effects in consecutive vascular sections of skeletal muscle

Humoral and neurogenic beta-adrenergic dilatation that influenced the resistance function, the capillary exchange function, and to some extent the capacitance function was demonstrated in the vascular bed of cat skeletal muscle. The beta-adrenergic effects were mainly confined to the microcirculation, causing dilatation of the precapillary sphincters and the resistance vessels of small calibre. The microcirculatory effects were pronounced in response to epinephrine, but blood-borne and nerve-released norepinephrine also evoked marked effects. The beta-adrenergic inhibition of vascular tone in the microcirculation may serve in the intact organism to improve tissue nutrition by facilitating capillary diffusion exchange. It further seems to regulate transcapillary hydrodynamic exchange, partly by controlling the precapillary sphincters and the capillary hydrostatic pressure. The blood-borne catecholamines, especially epinephrine, also markedly affected total regional vascular resistance and thereby blood flow by dilator interaction with the concomitant alpha-adrenergic vasoconstrictor response.