A method is described for the isolation and cannulation of microvessels (12-112 micrometers) that permits study, in vitro, of their physiology and pharmacology. Vessels from the hamster cheek pouch, testis, and mesentery and from rat brain have been isolated at 4 degrees C with specially prepared instruments and viewed with an inverted microscope. The vessels were cannulated at one end by equipment developed for renal tubular perfusion. The uncannulated end of the vessel is sealed, and experiments on reactivity and mechanics are carried out at fixed intravascular pressures. The isolated microvessels studied have a modulus of elasticity that is consistent with that observed in large vessels, and they display similar maximal active tension development (approximately 10(6) dyn/cm2). Reactivity to norepinephrine, acetylcholine, and adenosine are in the normal range for microvessels. Spontaneous tone is present, as evidenced by stable tonic contractions as well as phasic contractions in the frequency range of 3-30/min. The vessels display stress activation (myogenic response) consisting of contraction in response to increased intraluminal pressure. Our findings suggest that this preparation will be very useful in elucidating the physiology and pharmacology of the resistance vessels in the terminal vasculature.

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