Binding of Muscarone by Extracts of Housefly Brain: Relationship to Receptors for Acetylcholine

The supernatant fluid fraction isolated by centrifugation from a homogenate of heads of houseflies bound muscarone reversibly, with a binding constant of 2·4 × 10 −6 m and an amount of 70 nmol/g of protein. Studies with 28 drugs demonstrated strong blockade by the 17 cholinergic agents, suggesting both nicotinic and muscarinic characteristics in the mode of binding. The binding appeared to involve acetylcholine receptors.