A guinea pig is dissected and a portion of its intestine is fixed in the modified Dales chamber to study the effects of some drugs on intestinal contractility. A substance X was infused in the broth following which the graph comes out as depicted. Substance X most closely resembles which of these substances?
Ans: A. Epinephrine
(Ref: Goodman Gilman 12/e p188, 285: Katzung 13/e p89, 12/e p90; KDT 7/e p132, 6/e p120)
- Graph showng decreased contractility after infusion of substance X.
- Intestinal muscles show increase in contractility on action of acetylcholine on M3 receptors whil
- epinephrine inhibits contraction.
- Hence, the substance X is likely to be a sympathomimetic drug, i.e. Epinephrine.