Regulation of [3H]perhydrohistrionicotoxin binding to Torpedo ocellata electroplax by effectors of the acetylcholine receptor

R. S. Aronstam, A. T. Eldefrawi, Isaac N Pessah

Research output: Contribution to journalArticle

65 Citations (Scopus)

Abstract

The specific binding of [3H]perhydrohistrionicotoxin ([3H]H12-HTX) to the ionic channel of the nicotinic receptor in membranes from the electric organ of the electric ray Torpedo ocellata was studied by use of a rapid filter assay. The time course of the binding was monitored and the initial rate of binding (i.e. within 30 s) was found to be increased up to several hundredfold by the presence of several receptor agonists in a dose-dependent manner. Receptor antagonists blocked this agonist-increased initial rate of binding. The presence of receptor antagonists, with the exception of α-bungarotoxin, also increased the initial rate of [3H]H12-HTX binding, though to a much lesser degree than agonists. Preincubation of the membrane with carbamylcholine reduced the initial rate of binding in a time-dependent manner. This was proposed to be due to receptor desensitization. Thus, it is suggested that the time course of [3H]H12-HTX binding to the ionic channel sites is influenced by the conformational state of the receptor-channel complex such that receptor activation, inactivation, and desensitization appear to be reflected in [3H]H12-HTX binding.

Original languageEnglish (US)
Pages (from-to)2843-2850
Number of pages8
JournalJournal of Biological Chemistry
Volume256
Issue number6
StatePublished - 1981
Externally publishedYes

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Torpedo
Cholinergic Receptors
Ion Channels
Membranes
Bungarotoxins
Nicotinic Receptors
Carbachol
Electric Organ
Assays
Chemical activation
perhydrohistrionicotoxin

ASJC Scopus subject areas

  • Biochemistry

Cite this

Regulation of [3H]perhydrohistrionicotoxin binding to Torpedo ocellata electroplax by effectors of the acetylcholine receptor. / Aronstam, R. S.; Eldefrawi, A. T.; Pessah, Isaac N.

In: Journal of Biological Chemistry, Vol. 256, No. 6, 1981, p. 2843-2850.

Research output: Contribution to journalArticle

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AB - The specific binding of [3H]perhydrohistrionicotoxin ([3H]H12-HTX) to the ionic channel of the nicotinic receptor in membranes from the electric organ of the electric ray Torpedo ocellata was studied by use of a rapid filter assay. The time course of the binding was monitored and the initial rate of binding (i.e. within 30 s) was found to be increased up to several hundredfold by the presence of several receptor agonists in a dose-dependent manner. Receptor antagonists blocked this agonist-increased initial rate of binding. The presence of receptor antagonists, with the exception of α-bungarotoxin, also increased the initial rate of [3H]H12-HTX binding, though to a much lesser degree than agonists. Preincubation of the membrane with carbamylcholine reduced the initial rate of binding in a time-dependent manner. This was proposed to be due to receptor desensitization. Thus, it is suggested that the time course of [3H]H12-HTX binding to the ionic channel sites is influenced by the conformational state of the receptor-channel complex such that receptor activation, inactivation, and desensitization appear to be reflected in [3H]H12-HTX binding.

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