Muscarinic receptors mediating suppression of the M‐current in guinea‐pig olfactory cortex neurones may be of the M2‐subtype

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Abstract
Guinea-pig olfactory cortical neurones in vitro were voltage clamped by means of a single intracellular microelectrode technique. Hyperpolarizing voltage commands from holding potentials between −40 to − 50 mV produced slow inward current relaxations reflecting deactivation of the M-current (IM). IM was reversibly suppressed by 30 μm muscarine or carbachol; this suppression was insensitive to pirenzepine (up to 300 nm) but was inhibited by gallamine (10–20 μm) or 4-diphenyl-acetoxy-N-methylpiperidine (100, 500 nm), suggesting the involvement of the M2-type muscarinic receptor.