Abstract
Two properties were found to distinguish neuronal from muscle nicotinic acetylcholine receptors (nAChRs). First, neuronal nAChRs have a greater Ca
2+ permeability. The high Ca
2+ flux through neuronal nAChRs activates a Ca
2+-dependent CI
− conductance, and the Ca
2+ to Cs
+ permeability ratio (
P
Ca
P
Cs
) is 7 times greater for neuronal than for muscle nAChRs. A second difference between the receptor types is that neuronal nAChRs are potently modulated by physiological levels of external Ca
2+. Neuronal nAChR currents are enhanced by external Ca
2+ in a dose-dependent manner. The results indicate that changes in extracellular Call modulate neuronal nAChRs and may modulate cholinergic synapses in the CNS. Also, activation of neuronal nAChRs produces a significant influx of Ca
2+ that could be an important intracellular signal.
