Stoichiometry for Activation of Neuronal α7 Nicotinic Receptors

Neuronal α7 nicotinic receptors elicit rapid calcium influx in response to acetylcholine (ACh) or its product choline. They contribute to cognition, synaptic plasticity, and neuroprotection, and have been implicated in neurodegenerative and neuropsychiatric disorders. α7, however, often localizes distal to sites of nerve-released ACh, binds ACh with low affinity, and thus elicits its biological response with low agonist occupancy. To assess function of α7 when neurotransmitter occupies fewer than five of its identical binding sites, we measured open-channel lifetime of individual receptors in which four of the five ACh binding-sites were disabled.