Techniques to study the pharmacodynamics of isolated large and small blood vessels

Abstract

Techniques are described for the mounting of large artery and vein ring segments on wire hooks in an organ bath chamber. Each vessel is set to normalised conditions of passive force directly determined from its circumferential length-tension relationship. This rigorous set up follows the normalisation routine established by Mulvany and Halpern for small resistance arteries mounted under isometric conditions on a wire myograph. Techniques for electrical field stimulation, and simultaneous force and membrane potential (Em), are described. An example of electrical field stimulation is given for the unravelling of the role of ATP in sympathetic co-transmission in rat mesenteric small arteries. Other techniques described include isobaric, isotonic mounting of small vessels, their morphology and receptor characterisation. Examples include human buttock skin arteries, small coronary arteries (CAs), and vasa vasorum arteries taken at coronary bypass graft operations. The underlying philosophy is that every segment of blood vessel constituting the intact resistance bed has its own pharmacology. There is no 'ideal' preparation. Whether the vessel is studied under isometric, isotonic, or isobaric conditions, the experimentalist must be wary of the influence of the methodology on the pharmacodynamics. These influences may not be the same between normal and diseased vessels.