Beta-adrenergic control of resistance in individual vessels in rabbit tenuissimus muscle.

The microvascular responses to topically applied isoproterenol and to epinephrine in the intact and beta-adrenoceptor-blocked microcirculation were studied in the rabbit tenuissimus muscle by direct intravital microscopy. The main feeding arterioles in this muscle supply two vascular areas, the muscle capillaries and the adjacent connective tissue. beta-Adrenergic stimulation with isoproterenol and epinephrine dilated the transverse arterioles that supply muscle and connective tissues, whereas their first-order side branches (terminal arterioles), which only supply the muscle capillaries, were little affected. Flow measurements were made at two different sites in the transverse arterioles to determine the relative changes in muscle capillary flow and connective tissue flow. These measurements showed that beta-adrenergic stimulation caused a fractional redistribution of microvascular blood flow from the muscle tissue proper to the adjacent connective tissue.