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1.
The activity of the muscarinic cholinergic system (acetylcholine, ACh; acetylcholinesterase, AChE; choline acetyltransferase, ChAT; muscarinic acetylcholine receptors) was studied in the carp brain. The ACh content (13.9 ± 1.1 nmol/g wet tissue) was estimated by gas chromatography after microwave irradiation focused to the head. The AChE and ChAT activities were 153 ± 13 nmol/min/mg protein and 817 ± 50 pmol/min/mg protein, respectively. The characteristics of [3H](−)quinuclidinyl benzilate ([3H](−)QNB) and [3H]pirenzepine ([3H]PZ) binding were also studied in brain membranes. Their specific binding was linearly dependent on the protein content and they appeared to bind with high affinity to a single, saturable binding site. A dissociation constant (Kd) of 47 ± 6.3 pM and a maximum number of binding sites (Bmax) of 627 ± 65 fmol/mg protein were obtained for [3H](−)QNB, with a Kd value of 3.85 ± 0.67 nM and a Bmax value of 95.3 ± 6.25 fmol/mg protein for [3H]PZ binding. The [3H]PZ binding amounted to only 15% of the [3H](−)QNB-labeled sites, as estimated from the ratio of the Bmax values of [3H](−)QNB and [3H]PZ, suggesting a low density of M1 subtype. Atropine sulfate, atropine methylnitrate and PZ inhibited the binding of both radioligands with Hill slopes (nH) close to unity. The nH value of AF-DX 116 was close to 1 against [3H](−)QNB binding, while it was 0.75 against [3H]PZ binding. The displacement curves of oxotremorine and carbachol were shallow for the binding of both radioligands. The rank order of potency of muscarinic ligands against [3H](−)QNB binding (Ki nM) was atropine sulfate (0.55) > atropine methylnitrate (1.61) > PZ (61.19) > oxotremorine (156.3) > AF-DX 116 (307) > carbachol (1301), while in the case of [3H]PZ binding it was atropine sulfate (0.24) > atropine methylnitrate (0.34) > PZ (10.38) > AF-DX 116 (55.87) > oxotremorine (62.79) > carbachol (1696). The results indicate the presence of a well-developed muscarinic cholinergic system with predominantly M2 receptors in the carp brain. 相似文献
2.
K.M. Boje P. Skolnick J. Raber R.T. Fletcher G. Chader 《Neurochemistry international》1992,20(4):473-486
In the mammalian brain, the
(NMDA) subtype of glutamate receptor is coupled to a cation channel and a strychnine-insensitive glycine receptor. The present paper demonstrates the presence of NMDA receptor-coupled strychnine-insensitive glycine receptors in embryonic chick retina. Both glycine and 1-aminocyclopropanecarboxylic acid (ACPC) exhibited similar potencies (271 ± 39 vs 247 ± 39 nM, respectively) as inhibitors of strychnine-insensitive [3H]glycine binding to retinal membranes. Moreover, glycine and ACPC enhanced [3H]MK-801 binding to sites within the NMDA-coupled cation channel in retinal membranes with potencies comparable to those reported in rat brain. While the potency of ACPC was significantly higher than glycine (EC50 54±12 vs 256±57 nM, P < 0.02) in this measure, there were no significant differences in the maximum enhancement (efficacy) of [3H]MK-801 binding by these compounds. Since glycine appears to be required for the operation of NMDA-coupled cation channels, we examined the effects of glycine and ACPC on NMDA-induced acute excitotoxicity in the 14-day embryonic chick retina. Histological evaluation of retina revealed that either ACPC (10–100 μM) or glycine (200 μM) attenuated NMDA- induced (200 μM) retinal damage, and a combination of these agents produced an enhanced protection against acute NMDA toxicity. ACPC (100 μM), but not MK-801 (1 μM) also afforded a modest protection against kainate-induced (25 μM) retinal damage. These findings demonstrate that while strychnine-insensitive glycine receptors are present in embryonic chick retina, occupation of these sites does not augment the cytotoxic actions of NMDA. Moreover, the ability of ACPC and glycine to attenuate NMDA-induced cytotoxicity does not appear to be mediated through occupation of these sites. 相似文献
3.
Yukiko Shimizu Carol Yarborough Yoshio Osawa 《The Journal of steroid biochemistry and molecular biology》1993,44(4-6):651-656
In order to better understand the function of aromatase, we carried out kinetic analyses to asses the ability of natural estrogens, estrone (E1), estradiol (E2), 16-OHE1, and estriol (E3), to inhibit aromatization. Human placental microsomes (50 μg protein) were incubated for 5 min at 37°C with [1β-3H]testosterone (1.24 × 103 dpm 3H/ng, 35–150 nM) or [1β-3H,4-14C]androstenedione (3.05 × 103 dpm 3H/ng, 3H/14C = 19.3, 7–65 nM) as substrate in the presence of NADPH, with and without natural estrogens as putative inhibitors. Aromatase activity was assessed by tritium released to water from the 1β-position of the substrates. Natural estrogens showed competitive product inhibition against androgen aromatization. The Ki of E1, E2, 16-OHE1, and E3 for testosterone aromatization was 1.5, 2.2, 95, and 162 μM, respectively, where the Km of aromatase was 61.8 ± 2.0 nM (n = 5) for testosterone. The Ki of E1, E2, 16-OHE1, and E3 for androstenedione aromatization was 10.6, 5.5, 252, and 1182 μM, respectively, where the Km of aromatase was 35.4 ± 4.1 nM (n = 4) for androstenedione. These results show that estrogens inhibit the process of andrigen aromatization and indicate that natural estrogens regulate their own synthesis by the product inhibition mechanism in vivo. Since natural estrogens bind to the active site of human placental aromatase P-450 complex as competitive inhibitors, natural estrogens might be further metabolized by aromatase. This suggests that human placental estrogen 2-hydroxylase activity is catalyzed by the active site of aromatase cytochrome P-450 and also agrees with the fact that the level of catecholestrogens in maternal plasma increases during pregnancy. The relative affinities and concentration of androgens and estrogens would control estrogen and catecholestrogen biosynthesis by aromatase. 相似文献
4.
Gary L. Wenk Kathrin L. Engisch Lisa D. McCall Susan J. Mitchell Thomas G. Aigner Robert L. Struble Donald L. Price David S. Olton 《Neurochemistry international》1986,9(4):557-562
The present study investigated the effects of damage to the basal forebrain cholinergic system upon [3H]ketanserin binding in the neocortex and hippocampus of monkeys. [3H]Ketanserin specifically binds to serotonin type-2 receptor sites. Lesions were placed in the medial septal area, nucleus basalis, or both regions. Ten months later, [3H]ketanserin binding was increased in the neocortex, but not in the hippocampus, while levels of choline acetyltransferase (acetyl-CoA: choline O-acetyltransferase, EC 2.3.1.6) activity decreased in the neocortex and hippocampus. Changes in the levels of choline acetyltransferase and [3H]ketanserin binding were correlated significantly in the neocortex (r = −0.64, P < 0.025), but not in the hippocampus. The data suggest that degeneration of the basal forebrain cholinergic system may alter serotonergic function in the neocortex. 相似文献
5.
Previously, we have shown that substitution of Pro2 for cis-2-aminocyclopentanecarboxylic acid, ACPC in endomorphin-2 results in an analogue with greatly augmented proteolytic stability, high μ-opioid receptor affinity and selectivity. We now report the synthesis and biochemical characterization of [3H][(1S,2R)ACPC2]endomorphin-2 with a specific activity of 1.41 TBq/mmol (38.17 Ci/mmol). Specific binding of [3H][(1S,2R)ACPC2]endomorphin-2 was saturable and of high affinity with an equilibrium dissociation constant, Kd = 1.80 ± 0.21 nM and receptor density, Bmax = 345 ± 27 fmol × mg protein−1 at 25 °C in rat brain membranes. Similar affinity values were obtained in kinetic and displacement assays. Both Na+ and Gpp(NH)p decreased the affinity proving the agonist character of the radioligand. [3H][(1S,2R)ACPC2]endomorphin-2 retained the μ-specificity of the parent peptide. The new radioligand will be a useful tool to map the topographical requirements of μ-opioid peptide binding due to its high affinity, selectivity and enzymatic stability. 相似文献
6.
7.
Ethanol (15% v/v) was administered in the drinking water to male Wistar rats over period of 3 months. Binding properties of muscarinic receptors were studied in synaptosomes from selected brain areas using [3H]quinuclidinyl benzilate and its displacement by the selective antagonist, pirenzepine and the agonist, carbachol. Dissociation constants (Kd) of all three ligands in the cerebral cortex, hippocampus and striatum of ethanol-treated groups did not differ from those in controls. Density of [3H]quinuclidinyl benzilate binding sites in the cortex of ethanol-treated animals was approx. 50% higher than in controls (2.06 ± 0.2 and 1.32 ± 0.2 pmol/mg of protein respectively, mean ± SD, n = 6, P < 0.001). This was largely attributable to an increase in M1 binding sites as shown by pirenzepine displacement studies. In the hippocampus and striatum binding capacity of muscarinic receptors was not affected by ethanol treatment. Synthesis of acetylcholine in cerebral cortex prisms from ethanol-treated animals was not inhibited under resting conditions, but stimulation of synthesis by high K+ concentration was significantly altenuated by comparison with controls. These results suggest that chronic ethanol consumption induces changes in cholinergic neurotransmission in selected brain areas. 相似文献
8.
The influence of lipid peroxidation on 5-HT2 receptor binding was examined in prefrontal cortex membranes from sheep brain. Lipid peroxidation was induced with ascorbic acid and ferrous sulphate and measured by the thiobarbituric acid method. In lipid-peroxidized membranes, [3H]ketanserin specific binding was inhibited. The Bmax values decreased by 80%, from 50.1±3.5 fmol/mg protein in control membranes to 10.1±2.0 fmol/mg protein in peroxidized membranes, indicating a decrease in the number of 5-HT2 binding sites. However, the KD values for the [3H]ketanserin specific binding did not significantly change. In order to further characterize [3H]ketanserin binding, the inhibition potency (IC50 values) of antagonists or agonists of serotonin and dopamine receptors for [3H]ketanserin specific binding was determined. In control membranes, the order of the inhibition potency of the drugs tested was the following: ketanserin (−log [IC50] = 8.56±0.70) ritanserin (−log [IC50] = 8.13±0.30) methysergide (−log [IC50] = 7.42±0.50) spiperone (−log [IC50] = 7.23±0.18) serotonin (−log [IC50] = 6.99±0.65) haloperidol (−log [IC50] = 6.95±0.65) dopamine (−log [IC50] = 5.82±0.76). After membrane lipid peroxidation, the IC50 value for ritanserin was significantly increased, suggesting a decreased capacity for displacing [3H]ketanserin specific binding. Other antagonists of 5-HT2 receptors showed apparent increases in IC50 values upon peroxidation, whereas spiperone was shown to be the most potent drug (−log [IC50] = 7.19±1.06) in inhibiting [3H]ketanserin specific binding. A decrease in polyunsaturated fatty acids, namely docosahexaenoic acid (22:6) was also observed in peroxidized membranes. These results indicate a modulating role of the surrounding lipids and of the physical properties of the membranes on the binding activity of 5-HT2 receptors upon the lipid peroxidation process, which can be involved in the tissue impairment that occurs during the aging process and in post-ischemic situations. 相似文献
9.
Gino Giannaccini Laura Betti Massimo Correani Marco Dini Laura Giusti Antonio Lucacchini 《Neurochemistry international》1997,31(6):781-787
The distribution and the pharmacological properties of the binding of the benzodiazepine receptor antagonist [3H]-Ro 15–1788 (8-fluoro-3-carboethoxy-5,6-dihydro-5-methyl-6-oxo-4H imidazol [1,5-a] 1,4 benzodiazepine) were compared in some brain membranes of the saltwater teleost fish, Mullus surmuletus: only a single population of [3H]-Ro 15–1788 binding sites was detected. The binding was saturable and reversible with a high affinity, revealing a significant population of binding sites (Kd value of 2.1 ± 0.2 nM and Bmax value of 1400-900 fmol mg−1 of protein, depending on fish length). The highest concentration of benzodiazepine recognition sites labelled with [3H]-Ro 15–1788 was present in the optic lobe and the olfactory bulb and the lowest concentration was found in the medulla oblongata, cerebellum and spinal cord. In order to explore behavioural selectivity as a consequence of multiple receptor subtypes, six benzodiazepine receptor ligands, flunitrazepam (5-(2-fluoro-phenyl)-1,3,dihydro-1-methyl-7-nitro-2H-1,4-benzodiazepine-2-one), alpidem, (N,N-dipropyl-6-chloro-2-(4-chlorophenyl) imidazo [1,2-a] pyridine-3-acetamide) zolpidem {N,N,6, trimethyl-2-(4-methyl-phenyl) imidazo [1,2-a] pyridine-3-acetamide hemitartrate}, methyl β carboline-3-carboxylate (βCCM), Ro 15–1788 and Ro 5–4864 (4′-chlorodiazepam), were tested in vitro by binding of [3H]-Ro 15–1788 to membrane preparations from various brain areas of Mullus surmuletus. Displacement studies showed a similar rank order of efficacy of various unlabelled ligands. In all regions of the brain and in the spinal cord, GABA potentiate [3H]-flunitrazepam binding in a similar order, suggesting that the BDZ recognition sites are part of the GABAA receptor structure. These results suggest that central-type benzodiazepine receptors are present in one class of benzodiazepine binding sites in the saltwater teleost fish brain of Mullus surmuletus (type I-like). Here we report initial evidence of homogeneity of subtypes of central benzodiazepine receptors in the spinal cord of the saltwater teleost fish, Mullus surmuletus. 相似文献
10.
Xiao Zhang Ze-Hui Gong Karl Johan Fasth Bengt Lngstrm Agneta Nordberg 《Neurochemistry international》1998,32(5-6):435-441
The interaction of the nicotinic agonist (R,S)-3-pyridyl-1-methyl-2-(3-pyridyl)-azetidine (MPA) with different nicotinic acetylcholine receptor (nAChR) subtypes was studied in cell lines and rat cortex. MPA showed an affinity (Ki = 1.21 nM) which was higher than anatoxin-a > (−)-nicotine > (+)-[R]nornicotine > (−)-[S]nornicotine > and (+)-nicotine, but lower than cytisine (Ki = 0.46 nM) in competing for (−)-[3H]nicotine binding in M10 cells, which stably express the recombinant 4β2 nAChR subtype. A one-binding site model was observed in all competing experiments between (−)-[3H]nicotine binding and each of the agonists studied in M10 cells. MPA showed a 13-fold higher affinity for (−)-[3H]nicotine binding sites compared to the [3H]epibatidine binding sites in rat cortical membranes. In human neuroblastoma SH-SY5Y cells, which predominantly express the 3 nAChR subunit mRNA, MPA displaced [3H]epibatidine binding from a single population of the binding sites with an affinity in the same nM range as that observed MPA in displacing [3H]epibatidine binding in rat cortical membranes. Chronic treatment of M10 cells with MPA significantly up-regulated the number of (−)-[3H]nicotine binding sites in a concentration dependent manner. Thus MPA appears to have higher affinity to 4-subunit containing receptor subtype than 3-subunit containing receptor subtype of nAChRs. Furthermore MPA binds to 4β2 receptor subtype with higher affinity than (−)-nicotine and behaves, opposite to cytisine, as a full agonist in up-regulating the number of nAChRs. © 1998 Elsevier Science Ltd. All rights reserved. 相似文献
11.
Anna Siniscalchi Donata Rodi Stefania Gessi Franca Campi Pier A. Borea 《Neurochemistry international》1999,34(6):517-522
The effects of brain ischemia on the maximum binding capacity (Bmax) and affinity (Kd) of A1 receptors were studied in the rat cerebral cortex, with an in vitro approach. The results were correlated with changes in 3H-adenosine release, studied under identical experimental conditions. Fifteen minutes of in vitro ‘ischemia’ (hypoxic, glucose-free medium) induced a significant increase in both Bmax (2398±132 fmol/mg protein, 151% of the control, P<0.05) and in Kd (2.43±0.12 nM, 161% of the control, P<0.01). At the same time, an increase in tritium efflux from [3H]-adenosine labeled cerebral cortex slices to 324% of the control was observed. A trend toward normalization was evident 5–15 min after ‘reoxygenation’ (restoring normal medium), but the binding parameters were still altered after 60 min (Bmax 2110±82 fmol/mg protein, Kd 2.26±0.14 nM, P<0.01 vs the corresponding control) as was adenosine release (196% of the control). These findings suggest that the increased availability of adenosine and its receptors may be a defense mechanism against ischemic injury, while the reduced affinity of A1 receptors, possibly due to desensitization, may be a sign of ischemia-induced cellular damage. 相似文献
12.
The binding of [3H]mebendazole ([3H]MBZ) to tubulin in benzimidazole-susceptible (BZ-S) and benzimidazole-resistant (BZ-R) strains of Trichostrongylus colubriformis and Caenorhabditis elegans was examined in order to investigate the biochemical changes to tubulin that result in BZ resistance in parasitic and free-living nematodes. In both species the extent of [3H]MBZ binding to tubulin was significantly reduced in the BZ-R strain compared with the BZ-S strain. The decrease in [3H]MBZ binding in the BZ-R strain of each species was the result of a significant reduction in the amount of charcoal stable [3H]MBZ-tubulin complexes and was not related to a change in the association constant of the [3H]MBZ-tubulin interaction. [3H]MBZ binding to tubulin was temperature dependent, reaching maximum levels at 37°C in BZ-S T. colubriformis and 10°C in BZ-R T. colubriformis. Both the BZ-S and BZ-R strains of C. elegans displayed maximum [3H]MBZ binding at 4°C. Resistance ratios derived from the amount of [3H]MBZ binding in the BZ-S and BZ-R strains and in vitro development assays demonstrated that the temperature dependence and extent of drug binding was indicative of BZ resistance status and was species specific in the BZ-S isolates. These results indicate that biochemical differences exist in the binding of benzimidazole carbamates to tubulin in nematode species, and suggest that the susceptibility of the parasitic nematodes to the benzimidazole anthelmintics is the result of a unique high affinity and/or high capacity interaction ofbenzimidazole carbamates with tubulin. 相似文献
13.
A. E. Tory Masonis Michael P. McCarthy 《The Journal of steroid biochemistry and molecular biology》1996,58(5-6):551-555
The peripheral benzodiazepine receptor (PBR) is a mitochondrial protein involved in regulating steroid synthesis and transport. We report here the effects of androgenic/anabolic steroids (AAS) on the binding of the PBR-specific ligand [3H] PK11195 to male rat brain cortical synaptoneurosomes. Two synthetic AAS, stanozolol and 17β-testosterone cypionate (17β-cyp), significantly inhibited 1 nM [3H] PK11195 binding at concentrations greater than 5 and 25 μM, respectively. Stanozolol was the most effective inhibitor, reducing [3H] PK11195 binding by up to 75%, compared to only 40% inhibition by 17β-cyp, at 50 μM AAS concentration. Two other AAS, 17-methyltestosterone and nortestosterone decanoate, were incapable of inhibiting [3H] PK11195 binding at concentrations up to 50 μM. On the basis of Scatchard/Rosenthal analysis, [3H] PK11195 binds to two classes of binding sites, and the inhibition of [3H] PK11195 binding by stanozolol appears to be allosteric, primarily reducing binding to the higher affinity [3H] PK11195 binding site. These results, in combination with earlier studies indicating the direct effects of AAS on the function of additional central nervous system receptor complexes, suggest that the behavioral and psychological effects of AAS result from the interactions of AAS with multiple regulatory systems in the brain. 相似文献
14.
Uchida S Kurosawa S Fujino Oki T Kato Y Nanri M Yoshida K Yamada S 《Life sciences》2007,80(26):2454-2460
The present study was undertaken to characterize the binding activities of propiverine and its N-oxide metabolites (1-methyl-4-piperidyl diphenylpropoxyacetate N-oxide: P-4(N → O), 1-methyl-4-piperidyl benzilate N-oxide: DPr-P-4(N → O)) toward L-type calcium channel antagonist receptors in the rat bladder and brain. Propiverine and P-4(N → O) inhibited specific (+)-[3H]PN 200–110 binding in the rat bladder in a concentration-dependent manner. Compared with that for propiverine, the Ki value for P-4(N → O) in the bladder was significantly greater. Scatchard analysis has revealed that propiverine increased significantly Kd values for bladder (+)-[3H]PN 200–110 binding. DPr-P-4(N → O) had little inhibitory effects on the bladder (+)-[3H]PN 200–110 binding. Oxybutynin and N-desethyl-oxybutynin (DEOB) also inhibited specific (+)-[3H]PN 200–110 binding in the rat bladder. Propiverine, oxybutynin and their metabolites inhibited specific [N-methyl-3H]scopolamine methyl chloride ([3H]NMS) binding in the rat bladder. The ratios of Ki values for (+)-[3H]PN 200–110 to [3H]NMS were markedly smaller for propiverine and P-4(N → O) than oxybutynin and DEOB. Propiverine and P-4(N → O) inhibited specific binding of (+)-[3H]PN 200–110, [3H]diltiazem and [3H]verapamil in the rat cerebral cortex in a concentration-dependent manner. The Ki values of propiverine and P-4(N → O) for [3H]diltiazem were significantly smaller than those for (+)-[3H]PN 200–110 and [3H]verapamil. Further, their Ki values for [3H]verapamil were significantly smaller than those for (+)-[3H]PN 200–110. The Ki values of propiverine for each radioligand in the cerebral cortex were significantly (P < 0.05) smaller than those of P-4(N → O). In conclusion, the present study has shown that propiverine and P-4(N → O) exert a significant binding activity of L-type calcium channel antagonist receptors in the bladder and these effects may be pharmacologically relevant in the treatment of overactive bladder after oral administration of propiverine. 相似文献
15.
WAY–100635 is the first selective, silent 5–HT1A (5-hydroxytryptamine1A, serotonin-1A) receptor antagonist. We have investigated the use of [3H]WAY–100635 as a quantitative autoradiographic ligand in post-mortem human hippocampus, raphe and four cortical regions, and compared it with the 5–HT1A receptor agonist, [3H]8–OH–DPAT. Saturation studies showed an average Kd for [3H]WAY–100635 binding in hippocampus of 1.1 nM. The regional and laminar distributions of [3H]WAY–100635 binding and [3H]8–OH–DPAT binding were similar. The density of [3H]WAY–100635 binding sites was 60–70% more than that of [3H]8–OH–DPAT in all areas examined except the cingulate gyrus where it was 165% higher. [3H]WAY–100635 binding was robust and was not affected by the post-mortem interval, freezer storage time or brain pH (agonal state). Using [3H]WAY–100635, we confirmed an increase of 5–HT1A receptor binding sites in the frontal cortex in schizophrenia, previously demonstrated with [3H]8–OH–DPAT. Compared to [3H]8–OH–DPAT, [3H]WAY–100635 has two advantages: it has a higher selectivity and affinity for the 5–HT1A receptor, and it recognizes 5–HT1A receptors whether or not they are coupled to a G-protein, whereas [3H]8–OH–DPAT primarily detects coupled receptors. Given these considerations, the [3H]WAY–100635 binding data in schizophrenia clarify two points. First, they indicate that the elevated [3H]8–OH–DPAT binding seen in the same cases is attributable to an increase of 5–HT1A receptors rather than any other binding site. Second, the enhanced [3H]8–OH–DPAT binding in schizophrenia reflects an increased density of 5–HT1A receptors, not an increased percentage of 5–HT1A receptors which are G-protein-coupled. We conclude that [3H]WAY–100635 is a valuable autoradiographic ligand for the qualitative and quantitative study of 5–HT1A receptors in the human brain. 相似文献
16.
Met-enkephalin-Gly-Tyr (MEGY) is an endogenous peptide that binds to opioid sites in zebrafish and in rat brain homogenates. The aim of this work is to characterize the binding profile of this opioid ligand on two duplicate delta receptors from zebrafish, ZFOR1 and ZFOR4. Our results show that, while ZFOR1 presents one single binding site for [3H]-MEGY (KD = 4.0 ± 0.4 nM), the experimental data from ZFOR4 fit better to the two-site binding model (KD1 = 0.8 ± 0.2 nM and KD2 = 30.2 ± 10.2 nM). Two other MEGY synthetic analogues, (D-Ala2)-MEGY and (D-Ala2, Val5)-MEGY were also prepared and tested, together with the original peptide MEGY and other opioid ligands, in competition binding assays. While these peptides presented Ki values on the nanomolar range when using [3H]-MEGY as radioligand, these parameters were two orders higher in competition binding assays with the antagonist [3H]-diprenorphine. Functional [35S]GTPγS stimulation analysis has revealed that these two receptors can be activated by several opioid agonists. Our results prove that although the MEGY peptide acts as an agonist on ZFOR1 and ZFOR4, there are subtle pharmacological differences between these two delta opioid receptors from zebrafish. 相似文献
17.
The effects of γ-amino-n-butyric acid (GABA), (+)bicuculline, isoguvacine and 3-(4-chlorophenyl)-4-aminobutyrate [(±)baclofen] on the K-induced release of [3H]acetylcholine (ACh) were studied in the superior cervical ganglia of the rat in vitro. GABA and isoguvacine inhibited [3H]ACh release and these inhibitions were reversible by (+)bicuculline. Furthermore, the release of [3H]ACh was also inhibited by (±)baclofen. In receptor-binding studies, binding of [3H]GABA to membrane preparations from the superior cervical ganglia was inhibited by both (±)baclofen and (+)bicuculline. It is concluded that the inhibitory effect of GABA on the release of ACh can be mediated by GABAA(bicuculline-sensitive) and by GABAB (baclofen-activated) receptors. Our findings are compatible with the existence of a non-synaptic GABAergic inhibitory system involving GABAA and GABAB receptors on cholinergic nerve terminals in the superior cervical ganglion of rat. 相似文献
18.
Saxitoxin (STX) has proved useful in the isolation and characterization of vertebrate and invertebrate voltage-operated sodium channels. Membrane extracts from the nervous system of the cockroach Periplaneta americana contain a saturable component of specific [3H]STX binding. Scatchard analysis yields a KD of 0.84 nM, similar to that (3.0 nM) determined in electrophysiological studies on axons in the same tissue (Sattelle et al., 1979). The maximum number of binding sites, Bmax (8.25 pmol/mg protein), was higher than previously observed. The specific binding component was blocked by STX and tetrodotoxin (TTX), but not by scorpion (Leiurus quinquestriatus) venom, aconitine, veratridine, sea anemone toxin and deltamethrin, which act at different sites on the channel molecule. Unlabelled STX samples prepared from different sources (Mytilus, Saxidomus and Gonyaulax) were all effective as inhibitors of [3H]STX binding. Radiation inactivation was employed to determine the molecular target size of the [3H]STX binding molecule in membranes prepared from the cockroach nervous system. By this means Mr = 171,400 ± 25,000 was estimated for the insect sodium channel. 相似文献
19.
[3H]Neurotensin (NT) was found to bind specifically and with high affinity to crude membranes prepared from rat uterus. Scatchard analysis of saturation binding studies indicated that [3H]NT apparently binds to two sites (high affinity Kd 0.5 nM; low affinity Kd 9 nM) with the density of high affinity sites (41 fmoles/mg prot.) being about one-third that of the low affinity sites (100 fmoles/mg prot.). In competition studies, NT and various fragments inhibited [3H]NT binding with the following potencies (IC50): NT 8–13 (0.4 nM), NT 1–13 (4 nM), NT 9–13 (130 nM), NT 1–11, NT 1–8 (>100 μM). Quantitatively similar results were obtained using brain tissue. These findings raise the possibility of a role for NT in uterine function. 相似文献
20.
The potency of a series of opioid and non-opioid psychotomimetic drugs to inhibit the specific binding of [3H]PCP and ( + )-[3H]SKF-10,047 to rat cerebral cortical membranes was examined. ( + )-PCMP, the 3-methylpiperidino analog of PCP, was a potent inhibitor of the specific binding of both ligands. All of the other 12 compounds examined, however, displayed a 3-277-fold selectivity for either [3H]PCP or (+)-[3H]SKF-10,047 binding. These results suggest that although these opioid and non-opioid psychotomimetics bind to both sites, most have significantly different affinities. The binding sites for [3H]PCP appear to be distinct from the ‘sigma’ binding sites labeled with (+)-[3H]SKF-10,047.
SKF-10,047 Sigma receptor Phencyclidine Phencyclidine receptor Psychotomimetic activity 相似文献