Molecular Pharmacology, Vol 7, 104-110, Copyright © 1971 by the American Society for Pharmacology and Experimental Therapeutics

Binding of Five Cholinergic Ligands to Housefly Brain and Torpedo Electroplax

Relationship to Acetylcholine Receptors

¹ Section of Neurobiology and Behavior, Cornell University, Ithaca, New York 14850

The binding of radioactive muscarone, nicotine, decamethonium, dimethyl d-tubocurarine, and atropine to preparations of Torpedo electroplax and housefly brain has been studied at concentrations near 1 µM. Factors examined include binding constants and amounts, competition by cholinergic and noncholinergic drugs, reversibility, and sensitivity to hydrolytic enzymes. In Torpedo electroplax, muscarone, nicotine, and decamethonium appeared to bind, with binding constants between 0.4 and 2.5 µM, to the same macromolecules. These were phospholipoproteins present in the amount of 1.0-2.1 nmoles/g, fresh weight; their properties were similar to those of a nicotinic receptor. In the brain of the housefly, the same three ligands and also atropine appeared to bind, with binding constants between 0.2 and 3.2 µM, to the same macromolecules, which were proteins present in the amount of 2.2-3.2 nmoles/g, fresh weight. The latter exhibited properties similar to those of both nicotinic and muscarinic receptors.

Note:
ACKNOWLEDGMENT We are grateful to Mr. S. Rhine for computer analysis.

This article has been cited by other articles:

				M. E. Eldefrawi, A. G. Britten, and A. T. Eldefrawi Acetylcholine Binding to Torpedo Electroplax: Relationship to Acetylcholine Receptors Science, July 23, 1971; 173(3994): 338 - 340. [Abstract] [PDF]