Abstract
Acetylcholine (ACh) in low doses (0.1–1 μM) reversibly inhibits voltage-dependent activation of the “pacemaker” current,i f, in isolated sino-atrial node cells. This action is brought about by a negatively-directed shift of the current activation curve, opposite to that due to catecholamines on the same current. Thei f inhibition is anatagonized by atropine, indicating the involvement of muscarinic receptors. In cells incubated in pertussis toxin-containing solutions,i f does not respond to ACh, suggesting that G-proteins mediate the ACh-inducedi f depression. Further. ACh can inhibiti f following catecholamine-induced stimulation, but has a negligible effect oni f stimulated by forskolin, a direct activator of adenylate-cyclase. Our results indicate that ACh acts oni f by inhibiting basal adenylatecyclase activity.
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DiFrancesco, D., Tromba, C. Acetylcholine inhibits activation of the cardiac hyperpolarizing-activated current,i f . Pflugers Arch. 410, 139–142 (1987). https://doi.org/10.1007/BF00581906
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DOI: https://doi.org/10.1007/BF00581906