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Muscarinic Cholinergic Receptor‐Mediated Phosphoinositide Metabolism in Peripheral Nerve
Author(s) -
Day Nancy S.,
BertiMattera Lilia.,
Eichberg Joseph
Publication year - 1991
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.1471-4159.1991.tb03447.x
Subject(s) - muscarinic acetylcholine receptor , pirenzepine , inositol , endocrinology , medicine , chemistry , muscarinic acetylcholine receptor m1 , atropine , pertussis toxin , muscarinic acetylcholine receptor m3 , inositol phosphate , cholinergic , sciatic nerve , carbachol , receptor , g protein , biology , biochemistry
Few receptor‐mediated phenomena have been detected in peripheral nerve. In this study, th'e ability of the muscarinic cholinergic receptor agonist carbamylcholine to enhance phosphoinositide (PPI) breakdown in sciatic nerve was investigated by measuring the accumulation of inositol phosphates. Rat sciatic nerve segments were prelabeled with myo ‐[ 3 H]inositoI and then incubated either with or without carbamylcholine in the presence of Li + . [ 3 H]Inositol monophosphate ([ 3 H]IP) accumulation contained most of the radioactivity in inositol phosphates, with [ 3 H]inositol bisphosphate ([ 3 H]IP 2 ) and [ 3 H]inositoI trisphosphate ([ 3 H]IP 3 ) accounting for 7–8% and 1–2% of the total, respectively. In the presence of 100 γ M carbamylcholine, [ 3 H]IP accumulation increased by up to 150% after 60 min. The 50% effective concentration for the response was determined to be 20 γ M carbamylcholine and stimulated IP generation was abolished by 1 γ M atropine. Enhanced accumulation of IP 2 and IP 3 was also observed. Determination of the p A 2 values for the muscarinic receptor antagonists atropine (8.9), pirenzepine (6.5), AF‐DX 116 {11‐[[2‐[(diethylamino)methyl]‐1‐piperidinyl]acetyl]‐5,11 ‐dihydro‐6 H ‐pyrido[2,3‐ b ][1,4]benzodiazepin‐6‐one} (5.7), and 4‐diphenylacetoxy‐ N ‐methylpiperidinemethiodide (4‐DAMP) (8.6) strongly suggested that the M 3 muscarinic receptor subtype was predominantly involved in mediating enhanced PPI degradation. Following treatment of nerve homogenates and myelin‐rich fractions with pertussis toxin and [ 32 P]NAD + , the presence of an ADP‐ribosylated ∼40‐kDa protein could be demonstrated. The results indicate that peripheral nerve contains key elements of the molecular machinery needed for muscarinic receptor‐mediated signal transduction via the phosphoinositide cycle.