Calcium modulation and high calcium permeability of neuronal nicotinic acetylcholine receptors.
Two properties were found to distinguish neuronal from muscle nicotinic acetylcholine receptors (nAChRs). First, neuronal nAChRs have a greater Ca2+ permeability. The high Ca2+ flux through neuronal nAChRs activates a Ca(2+)-dependent Cl- conductance, and the Ca2+ to Cs+ permeability ratio (PCa/PCs) 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 Ca2+. Neuronal nAChR currents are enhanced by external Ca2+ in a dose-dependent manner. The results indicate that changes in extracellular Ca2+ modulate neuronal nAChRs and may modulate cholinergic synapses in the CNS. Also, activation of neuronal nAChRs produces a significant influx of Ca2+ that could be an important intracellular signal.
Vernino
S
S
Division of Neuroscience, Baylor College of Medicine, Houston, Texas 77030-3498.
Amador
M
M
Luetje
C W
CW
Patrick
J
J
Dani
J A
JA
D000311:Adrenal Glands / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D002417:Cattle; D002586:Cesium / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D002838:Chromaffin System / Q000502:physiology; D004553:Electric Conductivity; D007700:Kinetics; D008564:Membrane Potentials; D051379:Mice; D009132:Muscles / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009865:Oocytes / Q000378:metabolism; D010539:Permeability; D012313:RNA / Q000235:genetics; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D014981:Xenopus
D002712:Chlorides; D011978:Receptors, Nicotinic; D002586:Cesium; D012313:RNA; D002118:Calcium