a-Bungarotoxin Binding and Cholinergic Receptor Function on a Rat Sympathetic Nerve Line*

نویسندگان

  • JIM PATRICK
  • BILL STALLCUP
چکیده

A clonal rat sympathetic nerve cell line, PC12, binds iodinated cY-bungarotoxin. The binding is saturable and is inhibited by a variety of cholinergic agonists and antagonists. The pseudo-first order rate constant for binding is 2.1 x lo” Mm1 s-l at 22”. In contrast to the cu-bungarotoxin binding reaction found with muscle, the binding to PC12 is reversible with a first order rate constant of 4.9 x lo-” s-l at 37”. Toxin binds to an integral membrane component which sediments in sucrose gradients containing Triton X-100 with an apparent sedimentation coefficient of 10.5 S. The nicotinic acetylcholine receptor of PC12 was assayed by determining the agonist-induced increase in permeability to sodium ions. Using this assay, we determined the apparent binding constants for a variety of cholinergic ligands and found no correlation between their ability to affect cholinergic function and to inhibit binding of cY-bungarotoxin. Therefore, the site at which cholinergic ligands affect receptor function is different than the site at which cholinergic ligands inhibit toxin binding.

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تاریخ انتشار 2002