Electrical stimulation of the vagus nerve or injection of muscarine elicited peristalsis. It contains potentially deadly levels of muscarine. Most agonists for muscarine receptors are not selective for subtypes. Hence, it inhibits the effects of muscarine. Antimuscarinics such as atropine can be used as an antidote to muscarine. There are two mirror forms of muscarine, named&colon; 2S-muscarine and 2R-muscarine. Muscarinic receptors are so named because they are more sensitive to muscarine than to nicotine. The name muscarine is derived from the Latin word for the fly, musca. This allows muscarine to modulate cellular excitability via the membrane potential. The muscarine cholinergic receptor activates a G-protein when bound to extracellular ACh. "Inocybe" and "Clitocybe" contain muscarine concentrations up to 1.6%. Both "Omphalotus olivascens" and "Clitocybe dealbata" contain muscarine and are toxic. If muscarine is administered intravenously, muscarine can trigger acute circulatory failure with cardiac arrest. Muscarine is a nonselective agonist of the muscarinic acetylcholine receptors.