In vivo micro application of adrenaline to capillaries in frog mesentery

In-vivo studies were carried out on frog mesentery in order to determine the precise and specific actions of micropipette application of adrenaline on arterioles, precapillary sphincters and capillaries. A technique was employed, using liquid paraffin and micropipettes to deliver droplets to a particular microvessel; the droplets varied between 10-20 microns in diameter. All vessel types, including segments of capillaries, demonstrated constrictor responses to the local application of adrenaline. The time course of these constrictor events varied with the vessel type, with the sphincter being the most rapid in response.