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ACh, acting via
muscarinic receptors activates a nonselective cation current (IACh)
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in vascular and
visceral smooth muscles.
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At negative
potentials, most of the current through this conductance is carried by
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Na+;
the inward Na current is responsible for a significant part of the
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depolarization.
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IACh
is voltage dependent in many cells; current reverses near 0 mV
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IACh
is regulated by G proteins, and activation of IACh is blocked by
pertussis toxin
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Unclear whether
the conductance is a significant source of Ca2+
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