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1.
Specific 3H-diazepam binding to washed brain membranes from C57BL/6 mice of different age groups (3, 6, 12, 24 and 36 months) was studied in the absence and presence of 30 μM GABA. GABA treatment was found to be effective in decreasing the KD of 3H-diazepam binding of approximately 50% in all age groups tested (mean control KD = 6.5 nM, mean GABA-treated KD = 3.2 nM). No significant changes with age were observed in benzodiazepine receptor KD or Bmax in the presence or absence of GABA. 相似文献
2.
Drug competition profiles, effect of raphé lesion, and sodium dependency of the binding of two antidepressant drugs 3H-imipramine and 3H-mianserin to rat cerebral cortex homogenate were compared to examine whether the drugs bound to a common “antidepressant receptor.” Of the neurotransmitters tested, only serotonin displaced binding of both 3H-imipramine and 3H-mianserin. 3H-mianserin binding was potently displaced by serotonin S2 antagonists and exhibited a profile similar to that of 3H-spiperone binding. In the presence of the serotonin S2 antagonist spiperone, antihistamines (H1) potently displaced 3H-mianserin binding. 3H-Imipramine binding was displaced potently by serotonin uptake inhibitors. The order of potency of serotonergic drugs in displacing 3H-imipramine binding was not similar to their order in displacing 3H-spiperone or 3H-serotonin binding. Prior midbrain raphé lesions greatly decreased the binding of 3H-imipramine but did not alter binding of 3H-mianserin. Binding of 3H-imipramine but not 3H-mianserin was sodium dependent. These results show that 3H-imipramine and 3H-mianserin bind to different receptors. 3H-Imipramine binds to a presynaptic serotonin receptor which is probably related to a serotonin uptake recognition site, the binding of which is sodium dependent. 3H-Mianserin binds to postsynaptic receptors, possibly both serotonin S2 and histamine H1 receptors, the binding of which is sodium independent. 相似文献
3.
Evidence is provided to indicate that non-specific binding may in some cases be overlooked due to the non-saturating nature of this type of binding. Some of the theoretical aspects of competition for receptor binding sites are examined. 相似文献
4.
3H-Clozapine binds specifically and with high affinity (KD = 1.3 nM) to rat brain membranes. About two thirds of reversibly bound 3H-clozapine are displaced by hyoscyamine in a stereospecific manner, suggesting interaction of clozapine with muscarinic cholinergic receptors. Most of the remaining 3H-clozapine binding is stereospecifically inhibited by butaclamol, but this binding component seems not to be related to dopamine receptors. 相似文献
5.
6.
The characteristics of 3H-labeled imipramine and 3H-labeled paroxetine binding to human platelet membranes were determined at various temperatures between 0 and 37°C. Both paroxetine and imipramine probably bind to the same molecular complex in the platelet membrane, but the binding characteristics are different for the two molecules. The dissociation constant () for imipramine increases from 0.3 nM to 7.0 nM with increasing incubation temperature in a continuous way, whereas for paroxetine is almost constant, about 0.05 nM, between 0 and 19°C, and first begins to increase from 0.06 nM to 0.16 nM between 20 and 37°C. This suggests that the binding of paroxetine to the binding site induces a conformational change in the molecular complex of the binding site, whereas the binding of imipramine takes place without conformational changes in the binding site. 相似文献
7.
Trevor J. Rising David B. Norris Susan E. Warrander Terence P. Wood 《Life sciences》1980,27(3):199-206
Receptor binding studies have been carried out in guinea-pig cerebral cortex and gastric mucosa membrane preparations using 3H-cimetidine as the radioligand. The binding was found to be time dependent and saturable and confined to a single population of binding sites. However, the calculated KD values were different for the two tissues, did not correlate with those reported from classical pharmacological experimentation and there was either no or limited displacement by known H2 specific agonists. It was concluded that the observed high affinity binding site was probably related to an imidazole recognition site rather than the histamine H2 receptor. The need for careful evaluation of the data is stressed. 相似文献
8.
Randolph Y. Hampton Fedor Medzihradsky James H. Woods Patricia J. Dahlstrom 《Life sciences》1982,30(25):2147-2154
Phencyclidine (PCP) displaceable binding of 3H-PCP to glass-fiber filters was eliminated and total binding markedly reduced by initial treatment of the discs with 0.05% polyethyleneimine. Assessed with treated filters, unlabeled PCP displaced 3H-PCP in both rat and pigeon brain membranes with an EC50 of 1 μM. Of similar high inhibitory potency were dextrorphan, levorphanol, SKF 10047 and ketamine, while morphine, naloxone and etorphine had EC50 values higher then 1 mM. Using the dissociative anesthetic dexoxadrol and its inactive isomer levoxadrol as displacing agents, stereospecific binding of 3H-PCP was obtained in rat and pigeon brain membranes. The markedly higher potency of dexoxadrol, relative to levoxadrol, in displacing bound 3H-PCP is compatible with behavioral data for these enantiomers. However, they were equipotent in displacing 3H-PCP bound to glass-fiber filters in the absence of tissue. Heat denaturation, but not freezing, abolished stereospecific binding of 3H-PCP, which was also absent in rat liver membranes. The stereospecific binding component in brain displayed biphasic saturability at 60–70 nM and 300–400 nM, respectively. 相似文献
9.
The uptake and retention of 3H-serotonin, the level of endogenous serotonin and the high-affinity binding of 3H-imipramine were measured in the platelets of 23 patients suffering from alcoholic cirrhosis and 29 control volunteers. In the cirrhotic patients serotonin levels and 3H-serotonin accumulation were significantly decreased as compared to the control group. 3H-imipramine binding did not differ between the two groups. These results are discussed in relation to the postulated association between the 3H-imipramine binding site and the uptake mechanism for serotonin. 相似文献
10.
The effects of ascorbic acid on dopaminergic 3H-agonist receptor binding were studied in membrane homogenates of bovine anterior pituitary and caudate, and rat striatum. In all tissues virtually no stereospecific binding (defined using luM (+)butaclamol) of the 3H-agonists N-propylnorapomorphine (NPA), apomorphine, or dopamine could be demonstrated in the absence of ascorbic acid. Although levels of total 3H-agonist binding were three to five times greater in the absence than in the presence of 0.1% ascorbic acid, the increased binding was entirely non-stereospecific. Greater amounts of dopamine-inhibitable 3H-NPA binding could be demonstrated in the absence of 0.1% ascorbic acid, but this measure of “specific binding” was demonstrated not to represent dopamine receptor binding since several other catecholamines and catechol were equipotent with dopamine and more potent than the dopamine agonist (±)amino-6,7-dihydroxy-1,2,3,4-tetrahydronapthalene (ADTN) in inhibiting this binding. High levels of dopamine-displaceable 3H-agonist binding were detected in fresh and boiled homogenates of cerebellum, an area of brain which receives no dopaminergic innervation, further demonstrating the non-specific nature of 3H-agonist binding in the absence of ascorbic acid. These studies emphasize that under typical assay conditions ascorbic acid is required in order to demonstrate reversible and specific 3H-agonist binding to dopamine receptors. 相似文献
11.
[3H]-cocaine, [3H]-norcocaine, [3H]-benzoylecgonine and [3H]-benzoylnorecgonine were administered i.c. in equi-potent pharmacologic doses and the intracellular disposition and metabolism of each drug determined. Norcocaine and cocaine rapidly entered and egressed from the brain so that 4.8–6.1% of the radioactivity present in brain at one minute was observed at 30 minutes. The highest levels of subcellular radioactivity were generally found in the microsomal plus supernatant, followed by the nuclear and shocked mitochondrial fractions. No apparent localization of the radioactivity occured in synaptic membranes. The brain/plasma (B/P) ratio curves for cocaine and norcocaine were similar; however, the norcocaine values were considerably higher at each time interval. Benzoylecgonine and benzoylnorecgonine had higher comparative B/P ratios than cocaine or norcocaine and persisted in brain for a longer period of time so that 0.6–2.1% of the radioactivity present in brain at 1 hour was detected at 24 hours. Cocaine and norcocaine were extensively metabolized to the benzoylmetabolites. Benzoylecgonine was metabolized to benzoylnorecgonine and benzoylnorecgonine was unmetabolized. The brain disposition data and B/P ratios agreed quite well with the overall pharmacologic action of cocaine and its metabolites. 相似文献
12.
Dopamine receptors in the goldfish retina have been examined by binding studies using 3H-spiroperidol and 3H-domperidone as specific ligands, and by measuring retinal adenylate cyclase activities in the presence and absence of dopamine. Our results indicate that washed membranes from goldfish retinal homogenate bind a variety of dopamine agonists and antagonists with high affinities and with characteristics similar to those reported for the brain, with the exception that in this retina there is virtually no binding of the specific D2 receptor antagonist, 3H-domperidone. In addition, there is a very low basal activity of adenylate cyclase which can be greatly stimulated by dopamine, possibly reflecting a high degree of coupling between this enzyme and the dopamine receptor. Taken together, our findings indicate that the goldfish retina contains a high density of D1 type dopamine receptors and few, if any, D2 type receptors. 相似文献
13.
Intraperitoneal injection of phencyclidine before intravenous injection of [3H] Quinuclidinyl benzilate (QNE, 1.6 μg/kg) significantly increased the amount of radioactivity found in the brains of female C57BL/6J mice one hour after the 3H-QNB administration. This effect was found in hypothalamus, cortex, hippocampus and striatum and was decreased by pretreatment of the animal with atropine. The magnitude of the enhancement varied as a function of dose but did not change across the time span studied. These data are in contrast to our findings and those of others of inhibition of the specific binding of 3H-QNB to muscarinic cholinergic receptors by PCP . When atropine or PCP was administered and the tissue later analyzed , no effects of the drugs were observed on 3H-QNB binding. The reasons for the differences remain a matter of speculation. 相似文献
14.
3H-Isoguvacine, a gamma aminobutyric acid (GABA) agonist, has been shown to bind to a mouse forebrain synaptic membrane preparation. The specific binding is displaceable by GABA, muscimol and bicuculline but not by picrotoxin or diaminobutyric acid. Kinetic data suggest two binding affinities. Highest levels of binding are observed in the cerebellum, cortex and hippocampus. It is suggested that isoguvacine binds to GABA binding sites and therefore represents a new ligand for measuring GABA receptor binding. 相似文献
15.
In an attempt to characterize the brain histamine H2 receptor, experiments were undertaken to study the binding properties of (N-methyl-3H) -cimetidine, an H2 receptor antagonist, in rat brain membranes. Using a centrifugation assay, 3H-cimetidine binding having a Kd of 0.40μM and a Bmax of 3.9 pmoles/mg protein was detected. Of fourteen anions and cations tested, one, Cu++, dramatically increased specific 3H-cimetidine binding, the increase being due mainly to a change in Bmax. Studies of substrate specificity for 3H-cimetidine binding revealed that Cu++, while not significantly affecting the potency of H2 receptor agonists and antagonists, dramatically decreases the potency of H1 receptor substances on the 3H-cimetidine binding site. In addition, both the relative and absolute potencies of various H2 receptor agonistsv and antagonists in displacing the ligand in the presence of Cu++ parallels their potencies in biological systems. These findings suggest that, under these conditions, 3H-cimetidine may be labelling a biologically relevant H2 binding site in brain and that Cu++ may regulate the substrate specificity for this site. The brain regional distribution and kinetic analysis of the binding suggest that it is not localized solely to the synaptic receptor for histamine, but may also be associated with histamine receptors at other neuronal, glial or vascular sites. 相似文献
16.
The characteristics of the specific binding of 3H-lisuride hydrogen maleate (3H-LHM) to homogenates of rat striatum and bovine frontal cortex tissue were investigated. In rat striatum 50% of 3H-LHM binding was inhibited potently by spiperone and haloperidol indicating a component of 3H-LHM binding to D2 dopamine receptors. Specific 3H-LHM binding was detected in rat striatum after selective blockade of the D2 dopamine component indicating specific 3H-LHM binding to other striatal sites. In bovine frontal cortex clonidine and serotonin competition curves for specific 3H-LHM binding included high affinity phases indicating alpha2 adrenergic and high affinity serotonergic components of binding. Blockade of the adrenergic component by 10?7M clonidine resulted in the specific 3H-LHM binding exhibiting distinctly serotonergic characteristics. Conversely, blockade of the serotonergic component by 2 × 10?7M serotonin resulted in the specific 3H-LHM binding exhibiting distinct alpha2 receptor characteristics. These data demonstrate the specific binding of 3H-LHM to alpha2 adrenergic receptors, to a high affinity serotonin site, and to D2 dopamine receptors. 相似文献
17.
James M. Schaeffer 《Life sciences》1980,27(13):1199-1204
Crude membrane fractions were prepared from rat retinae and used to study the specific binding of [3H]muscimol, a potent GABA agonist. Specific [3H]muscimol binding was enhanced 2–3 fold by pretreatment of the membranes with 0.025% Triton X-100. Two muscimol binding sites were demonstrated with KD values of 4.4 and 12.3 nM. GABA, muscimol, and 3-aminopropanesulfonic acid were the most potent inhibitors of specific [3H]muscimol binding with KI values of 15, 10, and 50 nM, respectively. These data are consistent with binding to the synaptic GABA receptor. 相似文献
18.
S.F. Muakkassah-Kelly J.W. Andresen J.C. Shih P. Hochstein 《Biochemical and biophysical research communications》1982,104(3):1003-1010
The effect of lipid peroxidation on two types of serotonin binding sites was investigated. Incubation of rat cortical membranes with an ascobate-dependent peroxidizing system resulted in the formation of malonyldialdehyde and significant decreases in the specific binding of [3H]serotonin and [3H]spiperone to the treated membranes. When ascorbate concentrations were varied from 0.025 to 6.0 mM, malonyldialdehyde production increased to a maximum at 0.5 mM ascorbate and then declined. Conversely, the specific binding of [3H]serotonin and [3H]spiperone decreased to a minimum at 0.5 mM ascorbate and then increased. Regression analysis of the data revealed that the decrease in the two binding sites was linearly correlated to lipid peroxidation. 相似文献
19.
William J. Ferrell Antonio Garces Etienne A. Desmyter 《Chemistry and physics of lipids》1976,16(4):276-284
Radioactive S-alkyl glycerol ethers have been synthesized with 35S, 14C and 3H labels as well as 3H/35S double labels.The synthesized compounds were converted to various derivatives which can serve to characterize the S-alkyl glycerol ethers. These included the isopropChemical analysis, IR, NMR, zonal TLC profile scans and GLC showed all the products to be > 99% pure.The GLC behaviour of the aldehyde and acetate derivatives of both S-alkyl glycerol ethers and O-alkyl glycerol ethers on EGSS-X was compared. 相似文献
20.
Higher concentrations of spiperone were required to compete against the binding of 3H-spiperone to calf caudate when higher concentrations of 3H-spiperone were used. The Cheng-Prusoff equation did not adequately apply to this hydrophobic ligand, since the Ki values varied directly with the 3H-spiperone concentration. The equation was only adequate and gave a constant Ki when the total concentrations of 3H-spiperone were replaced by the measured free concentrations. It is suggested that IC50 values are best reported as such, unless the free concentrations are actually determined directly. 相似文献