Nicotinic receptors that bind alpha-bungarotoxin on neurons raise intracellular free Ca2+.
Many populations of vertebrate neurons have a membrane component that binds alpha-bungarotoxin and cholinergic ligands. Despite the abundance of this component and its similarities to nicotinic receptors, its function has remained controversial. Using a fluorescence assay, we show here that activation of the component elevates the intracellular concentration of free Ca2+, demonstrating a receptor function for the toxin-binding component. Whole-cell voltage-clamp and intracellular recordings did not detect a significant current resulting from receptor activation, possibly because the currents were small or the receptors rapidly desensitized. The rise in intracellular free Ca2+ caused by the receptor was prevented by Ca2+ channel blockers. This suggests a signaling cascade likely to have important regulatory consequences for the neuron.
Vijayaraghavan
S
S
Department of Biology, University of California, San Diego, La Jolla 92093-0322.
Pugh
P C
PC
Zhang
Z W
ZW
Rathouz
M M
MM
Berg
D K
DK
D000818:Animals; D002038:Bungarotoxins / Q000378:metabolism* / Q000494:pharmacology; D002104:Cadmium / Q000494:pharmacology; D002118:Calcium / Q000032:analysis / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002642:Chick Embryo; D004305:Dose-Response Relationship, Drug; D005453:Fluorescence; D009474:Neurons / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D009532:Nickel / Q000494:pharmacology; D009538:Nicotine / Q000378:metabolism / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology; D011978:Receptors, Nicotinic / Q000378:metabolism* / Q000502:physiology*; D014403:Tubocurarine / Q000494:pharmacology
D002038:Bungarotoxins; D015220:Calcium Channels; D011978:Receptors, Nicotinic; D002104:Cadmium; D009538:Nicotine; D009532:Nickel; D009543:Nifedipine; D002118:Calcium; D014403:Tubocurarine