Effects of cholinergic compounds on the axon-Schwann cell relationship in the squid nerve fiber.
The effects of acetylcholine, carbamylcholine, D-tubocurarine, eserine, and alpha-bungarotoxin on the Schwann cell electrical potential of resting and stimulated squid nerve fibers were studied. Acetylcholine (10-7 M) and barbamylcholine (10-6 M) induce a prolonged hyper polarization in the Schwann cells of the unstimulated nerve fiber. In the presence of carbamylcholine (10-6 M) the behavior of the Schwann cell membrane to changes in the external potassium concentration approximates the behavior of an ideal potassium electrode. D-Tubocurarine (10-9 M) blocks the hyperpolarizing effects of nerve impulse trains and carbamylcholine (10-6 M), whereas at the same concentration eserine prolongs the Schwann cell hyperpolarizations induced by axon stimulation or by acetylcholine (10-7 M). alpha-Bungarotoxin (10-9M) also blocks the hyperpolarizing effect of nerve impulse trains and of carbamylcholine. D-Tubocurarine (10-5M) protects the Schwann cells against the irreversible action of alpha-bungarotoxin. These results show the existence of acetylcholine receptors in the Schwann cell membrane. Preliminary measurements of the binding of 125I-alpha bungarotoxin to the plasma membranes isolated from squid nerves also indicate the presence of acetylcholine receptors. These findings support the involvement of cholinergic mechanisms in the axon-Schwann cell relationship previously described.
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001369:Axons / Q000187:drug effects*; D001665:Binding Sites; D002038:Bungarotoxins / Q000378:metabolism / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D049832:Decapodiformes; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects*; D009474:Neurons / Q000187:drug effects; D010277:Parasympathomimetics / Q000494:pharmacology*; D010830:Physostigmine / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D012583:Schwann Cells / Q000187:drug effects*; D014403:Tubocurarine / Q000494:pharmacology
D002038:Bungarotoxins; D010277:Parasympathomimetics; D002217:Carbachol; D010830:Physostigmine; D000109:Acetylcholine; D011188:Potassium; D014403:Tubocurarine