Vipoxin both activates and antagonizes three types of acetylcholine response in Aplysia neurons

N. T. Slater, D. O. Carpenter, J. E. Freedman, S. H. Snyder

Research output: Contribution to journalArticlepeer-review

Abstract

The effects of vipoxin, a 13,000 Dalton protein component of Russell's viper venom on responses of voltage-clamped Aplysia neurons to acetylcholine (ACh) and monoamines has been studied. At low doses vipoxin reversibly antagonizes all 3 types of ionic response to ACh or carbachol, the order of susceptibility to blockade being Na+ > K+ > Cl-. High doses of vipoxin directly evoke the same ionic response on a given cell as that evoked by ACh. Responses to vipoxin are reversibly antagonized by cholinergic antagonists (e.g. hexamethonium, tetraethylammonium), but not by monoamine antagonists (e.g. bufotenine, ergometrine, cimetidine). In addition to activation of cholinergic responses, high doses of vipoxin also produce a reversible potentiation of responses to dopamine and 5-hydroxytryptamine on some cells. In contrast to its effects on Aplysia neurons, vipoxin has neither agonist nor antagonist actions at the frog neuromuscular junction. These results suggest that this venom protein acts as a partial agonist at molluscan ACh receptors and provides evidence for some phylogenetic difference between molluscan and vertebrate ACh receptors.

Original languageEnglish (US)
Pages (from-to)266-270
Number of pages5
JournalBrain research
Volume278
Issue number1-2
DOIs
StatePublished - Nov 14 1983

Keywords

  • Aplysia
  • Russell's viper venom
  • acetylcholine receptors
  • vipoxin

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Clinical Neurology
  • Developmental Biology

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