Neuronal acetylcholine receptors that bind alpha-bungarotoxin with high affinity function as ligand-gated ion channels.
Neuronal membrane components that bind alpha-bungarotoxin with high affinity can increase intracellular levels of free calcium, demonstrating the components function as nicotinic receptors. Though such receptors often contain the alpha 7 gene product, which by itself can produce ionotropic receptors in Xenopus oocytes, numerous attempts have failed to demonstrate an ion channel function for the native receptors on neurons. Using rapid application of agonist, we show here that the native receptors are ligand-gated ion channels which are cation selective, prefer nicotine over acetylcholine, and rapidly desensitize. Much of the calcium increase caused in neurons by the receptors under physiological conditions appears to result from their depolarizing the membrane sufficiently to trigger calcium influx through voltage-gated channels.
Zhang
Z W
ZW
Department of Biology, University of California, San Diego, La Jolla 92093-0357.
Vijayaraghavan
S
S
Berg
D K
DK
D000818:Animals; D002038:Bungarotoxins / Q000378:metabolism / Q000494:pharmacology*; D002104:Cadmium / Q000494:pharmacology; D002478:Cells, Cultured; D002642:Chick Embryo; D005071:Evoked Potentials / Q000187:drug effects; D005260:Female; D005728:Ganglia, Sympathetic / Q000502:physiology; D015640:Ion Channel Gating; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009538:Nicotine / Q000494:pharmacology*; D009865:Oocytes / Q000187:drug effects / Q000502:physiology; D011950:Receptors, Cholinergic / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology; D014982:Xenopus laevis
D002038:Bungarotoxins; D007473:Ion Channels; D011950:Receptors, Cholinergic; D002104:Cadmium; D013779:Tetrodotoxin; D009538:Nicotine