Drugs online research references
J Neurochem. 1985 Jan;44(1):240-6.
Muscarinic cholinergic receptors in human foetal brain: characterization and ontogeny of [3H]quinuclidinyl benzilate binding sites in frontal cortex.
Ravikumar BV, Sastry PS.
Twenty-two frontal cortices from normal human foetal brains of gestational ages ranging from 16 to 40 weeks and five postnatal brains ranging from 5 to 50 years were analysed for the ontogeny of muscarinic receptors using [3H]quinuclidinyl benzilate (QNB) as the ligand. QNB binding sites were shown to be stable up to 4 1/2 months of storage at -70 degrees C. QNB binding was characterized in frontal cortices of 28-week-old foetal brains as muscarinic receptors by the following criteria: (1) it was localised mainly in particulate fraction; (2) binding was saturable at a concentration of 1.5 nM; (3) the cholinergic antagonists atropine and scopolamine competed for the binding, with IC50 values of 1 and 0.8 nM, respectively. The agonists oxotremorine, carbachol, and pilocarpine gave IC50 values of 1, 15 and 18 microM, respectively. Nicotinic receptor ligands and noncholinergic drugs could not compete for the binding. Bimolecular association and dissociation rate constants for the reversible binding are 6.23 X 10(8) M-1 X min-1 and 2.0 X 10(-2) X min-1, respectively. The equilibrium dissociation constant is 33 pM. The KD obtained by saturation binding data is 103 pM. Ontogeny of muscarinic receptors showed three distinct phases: In phase I, they appear between 16 and 18 weeks [average concentration 109 fmol/mg protein of total particulate fraction (TPF)] and slowly increase up to 20 weeks (average concentration 147 fmol/mg protein TPF). Phase II is a lag period between 20 and 24 weeks at which time receptor concentration does not change perceptibly (average concentration (67 fmol/mg protein TPF).(ABSTRACT TRUNCATED AT 250 WORDS)
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Biochem Biophys Res Commun. 1984 Feb 29;119(1):163-7.
Muscarinic cholinergic receptors in a rat phaeochromocytoma cell line.
Cross AJ, Johnson JA, Frith C, Taylor GR.
The high affinity binding of the muscarinic ligand 3H-N-methylscopolamine (3H-NMS) to intact cells of the rat pheochromocytoma cell line PC12 was studied. A single class of saturable binding sites was observed with a density of about 5000 sites per cell, and a pharmacological profile consistent with muscarinic receptors. The inhibition of 3H-NMS binding by the antagonist pirenzepine was of low affinity suggesting PC12 muscarinic receptors may be similar to those found on rat sympathetic nerve terminals.
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Jpn J Surg. 1984 Mar;14(2):122-6.
Muscarinic cholinergic receptors in human gastric mucosa.
Tokunaga T, Nishimura R, Akagi M.
Muscarinic cholinergic receptor sites in human gastric mucosa were analyzed directly by using radioligand binding techniques with the specific muscarinic antagonist 3H-quinuclidinyl benzilate (QNB) as ligand. Specific binding of 3H-QNB to membrane preparations from human gastric mucosa was saturable, of high affinity (Kd = 4.17 +/- 1.94 nM, Bmax = 0.37 +/- 0.04 pmol/mg protein) and selectively inhibited by muscarinic antagonists (atropine, scopolamine) and agonists (acetylcholine, pilocarpine). These findings provide direct evidence for the existence of muscarinic cholinergic receptors in human gastric mucosa. The specific 3H-QNB binding to its receptor was blocked by atropine but not by histamine, cimetidine, pentagastrin, or synthetic human gastrin. The muscarine and histamine H2-receptor, or muscarine and gastrin receptor, probably do not share the same locus.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6748384&dopt=Abstract
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