A STUDY OF DRUG RECEPTORS IN THE ISOLATED RABBIT AORTA STRIP.
Technical rept. for Apr-Jul 63,
CHEMICAL RESEARCH AND DEVELOPMENT LABS EDGEWOOD ARSENAL MD
Pagination or Media Count:
An investigation was made to determine whether the action of acetylcholine is caused by the release of catecholamine from stores in the aortic wall or whether there is a cholinoreceptive site in this tissue. Isotonic contractions were recorded using isolated helical strips of rabbit aorta suspended in a bath of 95 percent 0 sub 2and 5 percent CO sub 2- saturated, phosphate-buffered Krebs solution maintained at a constant temperature of 37 degrees C. Acetylcholine, epinephrine, and antagonists to each atropine, dichloroisoporterenol were added directly to the tissue-bathing fluid with a syringe. Epinephrine and acetylcholine, at dose levels used, have only excitatory effects on the isolated rabbit aorta. At no concentration of acetylcholine was a relaxing effect observed. The sensitivity of the muscle to epinephrine and to acetylcholine is in the ratio of 1100 the threshold concentration for epinephrine is 1 X 10 to the power of minus 8 M. The rabbit aorta has a distinct myogenic cholinoreceptive site, and the excitatory effect is not caused by a catecholamine releasing mechanism, which possibly exists in other parts of the vascular tree. Author