Muscarinic agonists block five different potassium conductances in guinea‐pig sympathetic neurones

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Abstract
Muscarinic excitation of sympathetic ganglion cells has usually been thought to result from inhibition of an outward K+ current, the M current, although in other neurones several conductances have been shown to be blocked by muscarinic agonists. We report that, as well as resting K+ conductance, all of four different K+ conductances, two voltage‐dependent (M currents and A currents) and two calcium‐dependent (responsible for slow and very slow afterhyperpolarizations), present in different sub‐types of guinea‐pig sympathetic neurones, are inhibited by the muscarinic agonists, bethanechol and muscarine. All of these effects increase neurone excitability and can lead to repetitive discharge.