Referenced in: none

Automatically associated channels: Kv10.1

Title: Distinction between high-affinity [3H]phencyclidine binding sites and muscarinic receptors in guinea-pig ileum muscle.

Authors: E E el-Fakahany, D J Triggle, A T Eldefrawi, M E Eldefrawi

Journal, date & volume: J. Pharmacol. Exp. Ther., 1984 May , 229, 447-54

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/6325665

Abstract
[3H]Phencyclidine ([3H]PCP) binding was studied in guinea-pig ileum muscle membranes. Specific binding of [3H]PCP was time dependent, reversible and saturable, with an equilibrium dissociation constant of 154 nM and maximum binding of 12.9 pmol/mg of protein at pH 9. Its pH dependency suggests that the unionized PCP is the pharmacologically active form. The binding site was on a protein which was sensitive to heat, proteolytic enzymes and the carboxylic group reagent dicyclohexylcarbodiimide, but insensitive to phospholipase A and C, concanavalin A, dithiothreitol and N-ethylmaleimide. Specific [3H]PCP binding was displaced effectively by several PCP analogs and Ca++ channel antagonists including verapamil, to which these sites had a high affinity. These high-affinity PCP-binding sites were found at a much higher concentration in the same membrane preparation than muscarinic receptor sites identified by their specific binding of [3H]quinuclidinyl benzilate. PCP bound to both sites, but with a lower affinity to the muscarinic receptor sites. The PCP and muscarinic receptor sites differed in their sensitivities to pH and drug specifities .