Accession Number : ADA033255


Title :   Binding of Alpha-Bungarotoxin to Single Identified Neurons of 'Aplysia' which have Different Ionic Responses to Acetylcholine,


Corporate Author : ARMED FORCES RADIOBIOLOGY RESEARCH INST BETHESDA MD


Personal Author(s) : Shain,W. G. , Jr. ; Greene,L. A. ; Carpenter,D. O.


Report Date : SEP 1976


Pagination or Media Count : 21


Abstract : Identifiable Aplysia neurons have one or more of three different ionic responses to acetylcholine, due to Na, Cl, and K conductance increases, respectively. The nature of the acetylcholine receptor mediating these three responses was studied using alpha-bungarotoxin. All three physiologic responses are blocked by alpha-bungarotoxin and I(125) alpha-bungarotoxin binds saturably to single neurons dissected from the ganglia. The apparent dissociation constant for I(125) alpha-bungarotoxin binding is not significantly different in neurons with different ionic response to acetylcholine. Most Na neurons, however, have a greater density of acetylcholine receptors. When studied electrophysiologically only the Na responses are blocked by hexamethonium. These observations are consistent with the view that Na, Cl, and K responses to acetylcholine are activated through a single class of acetylcholine receptors. The efficacy of hexamethonium in blocking toxin binding to all types of neurons suggests that it has a common binding site on all Aplysia acetylcholine receptors. Thus the inhibition of the Na response by hexamethonium may be a result of the binding to a site which prevent the conductance change rather than preventing acetylcholine from binding to its receptor.


Descriptors :   *VENOMS, *ACETYLCHOLINE, *CHEMORECEPTORS, NERVE CELLS, ELECTROLYTES, SNAKES, TOXINS AND ANTITOXINS, RADIOACTIVE ISOTOPES, SYNAPSIS.


Subject Categories : BIOCHEMISRTY


Distribution Statement : APPROVED FOR PUBLIC RELEASE