Tension response of mammalian muscle to intra-arterial acetylcholine

¹ National Institute of Neurological Diseases and Blindness, National Institutes of Health, Bethesda, Maryland

Using isometric tension recording of the tibialis anterior muscle of the cat, the response to intra-arterial acetylcholine injection was studied and compared to the response to electrical stimulation of the nerve. The amount of acetylcholine, the rate of injection and the volume of diluent injected are interrelated factors in the production of tension. Regardless of the amount and concentration of the acetylcholine injected, the contractile response of the muscle has a slower rate of rise and a longer duration than the response from single maximal impulse stimulation to the nerve and a maximal tension less than from a tetanic neural stimulation. The dose-response relationship between the injected acetylcholine and the resultant tension and its modification by curare are described. The steep portion of the dose-response curve was found to occur in most experiments between 0.5 and 6.0 µg. A method of supplying blood to the muscle is described which provides more reliable intermittent arterial occlusion during injection.