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Kinetic Effects of Terbium Ions on Muscarinic Acetylcholine Receptors of Murine Neuroblastoma Cells
Author(s) -
ElFakahany Esam E.,
Pfenning Michael,
Richelson Elliott
Publication year - 1984
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1984.tb02760.x
Subject(s) - carbachol , muscarinic acetylcholine receptor , chemistry , endocrinology , medicine , quinuclidinyl benzilate , muscarinic acetylcholine receptor m1 , receptor , terbium , biophysics , biology , biochemistry , ion , organic chemistry
Preincubation of murine neuroblastoma cells (clone NIE‐115) with terbium chloride resulted in a significant potentiation of carbachol‐mediated increase in cyclic GMP formation. This effect was accompanied by a shift of the peak response from 30 s to 120 s and a 6‐fold decrease in carbachol concentration producing half‐maximal responses, in addition to a significant increase in the Hill coefficient. Terbium ions also caused a significant decrease in the affinity and an increase in the maximum binding of [ 3 H]quinuclidinyl benzilate to muscarinic receptors, the change in affinity being mainly due to a decrease in the association rate. Preincubation of cells with 1 m M carbachol for 4 h (the desensitized state of the muscarinic receptor) resulted in a decrease in the ability of terbium to alter [ 3 H]quinuclidinyl benzilate binding. The effects of terbium reported here might be due to its affecting muscarinic receptor‐effector coupling, which is considered to be lost upon receptor desensitization.