Peripheral Markers of Muscarinic Receptors

摘要

The studies were designed to provide information regarding the biochemical andfunctional characteristics of muscarinic receptors on lymphocytes and on the possibility of the use of these receptors as markers of muscarinic receptors in tissues not accessible in humans. Such knowledge will assist in assessing the effect of exposure of humans to chemicals which affect the nervous system. An extensive characterization of muscarinic binding sites in rat lymphocytes was performed. A series of eight muscarinic antagonists and five agonists were tested for their ability to inhibit tritium labeled QNB binding to lymphocytes. The authors conclude that a binding site for tritium labeled QNB is present on rat splenic and circulating lymphocytes which has most of the pharmacological characteristics of muscarinic cholinergic receptors. The major difference appears to be a lower affinity of muscarinic antagonists between lymphocytes and the brain. The muscarinic receptors would be tentatively of the M2 type as suggested by the high affinity of oxotremorine, the low affinity of pirenzepine, the strong effect of GTP on agonist binding and the lack of stimulation of phosphoinositide metabolism by cholinergic agonist.