共查询到20条相似文献,搜索用时 31 毫秒
1.
B. Kenneth Koe Lorraine A. Lebel Carol B. Fox John E. Macor 《Journal of neurochemistry》1992,58(4):1268-1276
Abstract: 3-(1,2,5,6-Tetrahydro-4-pyridyl)-5- n -propoxyindole (CP-96,501) was found to be a more selective ligand at the serotonin 5-HT1B receptor than the commonly used 5-HT1B agonist, 3-(1,2,5,6-tetrahydro-4-pyridyl)-5-methoxyindole (RU 24969). In rat brain membranes, the tritiated derivative, [3 H]CP-96,501, was found to bind with a high affinity ( K D , 0.21 n M ) to a single binding site ( n H , 1.0). The receptor density of this site ( B max , 72 fmol/mg of protein) matched that of the 5-HT1B receptor determined with [3 H]5-HT. Competition curves of 16 serotonergic compounds in [3 H]CP-96,501 binding also indicated a single binding site. The rank order of their binding affinities with this new radioligand showed a high degree of correlation with their affinities at the 5-HT1B receptor determined with [3 H]5-HT or [125 I]iodocyanopindolol. Serotonergic compounds displayed competitive inhibition of [3 H]CP-96,501 binding. In the presence of 5'-guanylylimidodiphosphate [Gpp(NH)p], [3 H]CP-96,501 binding was reduced, while the potency of CP-96,501 to displace [125 I]iodocyanopindolol binding was also decreased. These findings are consistent with the agonist nature of CP-96,501. The results of this study suggest that [3 H]CP-96,501 is a useful agonist radioligand for the 5-HT1B receptor. 相似文献
2.
Anissa Abi-Dargham Marc Laruelle David T. Wong David W. Robertson† Daniel R. Weinberger Joel E. Kleinman 《Journal of neurochemistry》1993,60(2):730-737
Abstract: Binding of [3 H]LY278584, which has been previously shown to label 5-hydroxytryptamine3 (5-HT3 ) receptors in rat cortex, was studied in human brain. Saturation experiments revealed a homogeneous population of saturable binding sites in amygdala ( K D = 3.08 ± 0.67 n M, B max = 11.86 ± 1.87 fmol/mg of protein) as well as in hippocampus, caudate, and putamen. Specific binding was also high in nucleus accumbens and entorhinal cortex. Specific binding was negligible in neocortical areas. Kinetic studies conducted in human hippocampus revealed a K on of 0.025 ± 0.009 n M −1 min−1 and a K off of 0.010 ± 0.002 min−1 . The kinetics of [3 H]LY278584 binding were similar in the caudate. Pharmacological characterization of [3 H]LY278584 specific binding in caudate and amygdala indicated the compound was binding to 5-HT3 receptors. We conclude that 5-HT3 receptors labeled by [3 H]LY278584 are present in both limbic and striatal areas in human brain, suggesting that 5-HT3 receptor antagonists may be able to influence the dopamine system in humans, similarly to their effects in rodent studies. 相似文献
3.
David R. Luthin †Kevin S. Lee †David Okonkwo ‡Peijun Zhang ‡ Joel Linden 《Journal of neurochemistry》1995,65(5):2072-2079
Abstract: The A2a adenosine receptor agonist 2-[2-(4-amino-3-iodophenyl)ethylamino]adenosine is a potent coronary vasodilator. The corresponding radioiodinated ligand, [125 I]APE, discriminates between high- and low-affinity conformations of A2a adenosine receptors. In this study, [125 I]APE was used for rapid (24-h) autoradiography in rat brain sections. The pattern of [125 I]APE binding is consistent with that expected of an A2a -selective radioligand. It is highest in striatum, nucleus accumbens, and olfactory tubercle, with little binding to cortex and septal nuclei. Specific [125 I]APE binding to these brain regions is abolished by 1 µ M 2- p -(2-carboxyethyl)phenethylamino-5'- N -ethylcarboxamidoadenosine (CGS-21680) but is little affected by 100 n M 8-cyclopentyl-1,3-dipropylxanthine. Conversion of [125 I]APE to the corresponding arylazide results in [125 I]AzPE. The rank-order potency of compounds to compete for [125 I]AzPE binding in the dark is CGS-21680 > d -( R )- N 6 -phenylisopropyladenosine > N 6 -cyclopentyladenosine, indicating that it also is an A2a -selective ligand. Specific photoaffinity labeling by [125 I]AzPE of a single polypeptide (42 kDa) corresponding to A2a adenosine receptors is reduced 55 ± 4% by 100 µ M guanosine 5'- O -(3-thiotriphosphate) and 91 ± 1.3% by 100 n M CGS-21680. [125 I]APE and [125 I]AzPE are valuable new tools for characterizing A2a adenosine receptors and their coupling to GTP-binding proteins by autoradiography and photoaffinity labeling. 相似文献
4.
J. M. Scalzitti K. A. Berg S. A. Kratowicz J. G. Hensler 《Journal of neurochemistry》1998,71(4):1457-1463
Abstract: The regulation of 5-HT2A receptor expression by an antisense oligodeoxynucleotide, complementary to the coding region of rat 5-HT2A receptor mRNA, was examined in a cortically derived cell line and in rat brain. Treatment of A1 A1 variant cells, which express the 5-HT2A receptor coupled to the stimulation of phosphatidylinositol (PI) hydrolysis, with antisense oligodeoxynucleotide decreased the maximal stimulation of PI hydrolysis by the partial agonist quipazine and the number of 5-HT2A receptor sites as measured by the binding of 2-[125 I]-iodolysergic acid diethylamide. Treatment of cells with random, sense, or mismatch oligodeoxynucleotide did not alter the stimulation of PI hydrolysis by quipazine or 5-HT2A receptor number. Intracerebroventricular infusion of antisense, but not mismatch, oligodeoxynucleotide for 8 days resulted in a significant increase in cortical 5-HT2A receptor density and an increase in headshake behavior induced by the 5-HT2 receptor agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane. The density of cortical 5-HT2A receptors was not altered by administration of antisense oligodeoxynucleotide for 1, 2, or 4 days. We hypothesize that in brain this antisense oligodeoxynucleotide relieved some form of translational suppression, resulting in an increase in 5-HT2A receptor expression. 相似文献
5.
Eric M. Parker Darcy A. Grisel Lawrence G. Iben Robert A. Shapiro† 《Journal of neurochemistry》1993,60(1):380-383
Abstract: Molecular cloning of the rat and human 5-hydroxytryptamine1B (5-HT1B ) receptors has revealed that the primary amino acid sequence of these two receptors is >90% identical. Despite this high degree of primary sequence homology, these two receptors have significantly different pharmacological properties. A mutant human 5-HT1B receptor was constructed in which Thr355 was replaced by Asn, the corresponding residue at this position in the rat 5-HT1B receptor. The pharmacology of the mutant human 5-HT1B receptor was very similar to that of the rat 5-HT1B receptor. Specifically, the mutant receptor had much higher affinity for pindolol, [125 I]-iodocyanopindolol, propranolol, and CP-93,129 than the wild-type receptor. In contrast, the mutant had significantly lower affinity for sumatriptan, N,N -dipropyl-5-carboxamidotryptamine, 5-methoxy- N,N -dimethyltryptamine, methysergide, metergoline, and rauwolscine. These data suggest that a single amino acid difference at position 355 is responsible for the pharmacological differences between the rat and human 5-HT1B receptors. 相似文献
6.
Recent studies have indicated that the serotonin [5-hydroxytryptamine (5-HT)] 1E receptor, originally discovered in human brain tissue, is not expressed in rat or mouse brain. Thus, there have been few reports on 5-HT1E receptor drug development. However, expression of 5-HT1E receptor mRNA has been shown in guinea pig brain. To establish this species as an animal model for 5-HT1E drug development, we identified brain regions that exhibit 5-carboxyamidotryptamine, ritanserin, and LY344864 – insensitive [3 H]5-HT binding (characteristic of the 5-HT1E receptor). In hippocampal homogenates, where 5-HT1E receptor density was sufficiently high for radioligand binding analysis, 100 nM 5-carboxyamidotryptamine, 30 nM ritanserin, and 100 nM LY344864 were used to mask [3 H]5-HT binding at non-5-HT1E receptors. The K d of [3 H]5-HT was 5.7 ± 0.7 nM and is indistinguishable from the cloned receptor K d of 6.5 ± 0.6 nM. The affinities of 16 drugs for the cloned and hippocampal-expressed guinea pig 5-HT1E receptors are essentially identical ( R 2 = 0.97). These findings indicate that using these conditions autoradiographical distribution and signal transduction studies of the 5-HT1E receptor in guinea pig brain are feasible. Using the guinea pig as an animal model should provide important insights into possible functions of this receptor and the therapeutic potential of selective human 5-HT1E drugs. 相似文献
7.
Marc Laruelle Suzanne S. Giddings Yolanda Zea-Ponce Dennis S. Charney John L. Neumeyer Ronald M. Baldwin Robert B. Innis 《Journal of neurochemistry》1994,62(3):978-986
Abstract: Methyl 3β-(4-[125 I]iodophenyl)tropane-2β-carboxylate ([123 I]β-CIT) is a single photon emission computed tomographic radiotracer for in vivo labeling of dopamine (DA) and serotonin (5-HT) transporters. Single photon emission computed tomographic experiments in nonhuman primates showed that [123 I]β-CIT in vivo binding to DA transporters had a much slower washout than binding to 5-HT transporters. This observation was not predicted from previously published in vitro studies. These studies, performed at 22°C in nonphysiological buffer, reported similar affinity of [125 I]β-CIT for DA and 5-HT transporters. We now report [125 I]β-CIT binding parameters to fresh rat membranes at 22°C and 37°C, in a buffer mimicking the composition of cerebrospinal fluid. At both temperatures, binding to DA transporters was best fit by a twosite model, whereas binding to 5-HT transporters was compatible with one population of sites. At 22°C, [125 I]β-CIT showed similar affinity to high-affinity DA (0.39 n M ) and 5-HT transporter sites (0.47 n M ). Increasing the incubation temperature from 22°C to 37°C reduced binding to DA transporters by 60%, whereas binding to 5-HT transporters was only marginally affected. In vitro kinetic experiments failed to detect significant differences in on or off rates that could explain the observed in vivo kinetics. These experiments thus failed to explain [123 I]β-CIT in vivo uptake kinetics, suggesting the existence of specific factors affecting the in vivo situation. 相似文献
8.
Eric M. Parker Darcy G. Izzarelli Lore Lewis-Higgins Dawn Palmer Robert A. Shapiro 《Journal of neurochemistry》1996,67(5):2096-2103
Abstract: 5-Hydroxytryptamine elicits its physiological effects by interacting with a diverse group of receptors. Two of these receptors, the 5-HT1Dβ and the 5-HT1E receptors, are ∼60% identical in the transmembrane domains that presumably form the ligand binding site yet have very different pharmacological properties. Analysis of the pharmacological properties of a series of chimeric 5-HT1Dβ /5-HT1E receptors indicates that sequences in the sixth and seventh transmembrane domains are responsible for the differential affinity of 5-carboxamidotryptamine for these two receptors. More detailed analysis shows that two amino acid differences in the sixth transmembrane domain (Ile333 and Ser334 in the 5-HT1Dβ receptor, corresponding to Lys310 and Glu311 in the 5-HT1E receptor) are largely responsible for the differential affinities of some, but not all, ligands for the 5-HT1Dβ and 5-HT1E receptors. It is likely that these two amino acids subtly determine the overall three-dimensional structure of the receptor rather than interact directly with individual ligands. 相似文献
9.
Cecilie L. Licht ers B. Marcussen Gregers Wegener† David H. Overstreet‡ Susana Aznar Gitte M. Knudsen 《Journal of neurochemistry》2009,109(5):1363-1374
The 5-hydroxytryptamine (5-HT4 ) receptor may be implicated in depression and is a new potential target for antidepressant treatment. We have investigated the brain 5-HT4 receptor [3 H]SB207145 binding in the Flinders Sensitive Line rat depression model by quantitative receptor autoradiography, and related this to 5-HT transporter ( S )-[ N -methyl-3 H]citalopram binding. We also determined the regulation of 5-HT4 receptor binding by 1, 14, and 21 days of paroxetine administration and subchronic 5-HT depletion, and compared this with changes in 5-HT2A receptor [3 H]MDL100907 binding. In the Flinders Sensitive Line, the 5-HT4 receptor and 5-HT transporter binding were decreased in the dorsal and ventral hippocampus, and the changes in binding were directly correlated within the dorsal hippocampus. Chronic but not acute paroxetine administration caused a 16–47% down-regulation of 5-HT4 receptor binding in all regions evaluated including the basal ganglia and hippocampus, while 5-HT depletion increased the 5-HT4 receptor binding in the dorsal hippocampus, hypothalamus, and lateral globus pallidus. In comparison, the 5-HT2A receptor binding was decreased in the frontal and cingulate cortices after chronic paroxetine administration, and markedly reduced in several regions after 5-HT depletion. Thus, the 5-HT4 receptor binding was decreased in the Flinders Sensitive Line depression model and in response to chronic paroxetine administration. 相似文献
10.
Soluble amyloid-β peptide (Aβ) exists in the form of monomers and oligomers, and as complexes with Aβ-binding molecules, such as low-density lipoprotein receptor-related protein-1 (LRP-1) ligands. The present study investigated the effect of self-aggregation and LRP-1 ligands on the elimination of human Aβ(1–40) [hAβ(1–40)] from the rat brain across the blood–brain barrier. Incubation of [125 I]hAβ(1–40) monomer resulted in time-dependent and temperature-dependent dimer formation, and the apparent elimination rate of [125 I]hAβ(1–40) dimer was significantly decreased by 92.7% compared with that of [125 I]hAβ(1–40) monomer. Pre-incubation with LRP-1 ligands, such as activated α2-macroglobulin (α2M), apolipoprotein E2 (apoE2), apoE3, apoE4, and lactoferrin, reduced the elimination of [125 I]hAβ(1–40). By contrast, pre-administration of the same concentration of these molecules in the rat brain did not significantly inhibit [125 I]hAβ(1–40) monomer elimination. Purified [125 I]hAβ(1–40)/activated α2M complex and [125 I]activated α2M were not significantly eliminated from the rat brain up to 60 min. MEF-1 cells, which have LRP-1-mediated endocytosis, exhibited uptake of [125 I]activated α2M, and enhancement of [125 I]hAβ(1–40) uptake upon pre-incubation with apoE, suggesting that [125 I]activated α2M and [125 I]hAβ(1–40)/apoE complex function as LRP-1 ligands. These findings indicate that dimerization and LRP-1-ligand complex formation prevent the elimination of hAβ(1–40) from the brain across the blood–brain barrier. 相似文献
11.
Douglas W. Bonhaus Eric Stefanich Dana N. Loury Sherry A. O. Hsu Richard M. Eglen Erik H. F. Wong 《Journal of neurochemistry》1995,65(1):104-110
Abstract: Cooperation in the action of agonists suggests that there are multiple binding sites on 5-hydroxytryptamine3 (5-HT3 ) receptors. The purpose of this study was to characterize these binding sites and their interactions on both native and cloned 5-HT3 receptors. The affinities of competitive 5-HT3 receptor antagonists were similar regardless of whether the receptors were labeled with [3 H]RS-42358, [3 H]granisetron, or 1-( m -[3 H]chlorophenyl)biguanide ([3 H]mCPG). By contrast, the affinities of the agonists 5-HT, mCPG, and phenylbiguanide were approximately 10-fold higher when the receptors were labeled with [3 H]mCPG. The dissociation of [3 H]mCPG, [3 H]RS-42358, and [3 H]RS-25259, but not [3 H]granisetron, from both cloned and native 5-HT3 receptors was markedly slower in the presence of 5-HT or 2-methyl-5-HT than in the presence of antagonists such as RS-42358. This suggests that the binding of these agonists to unoccupied sites on the receptor can increase the receptor's affinity for prebound ligands and thereby slow their dissociation. These data support previous indications of positive cooperation among multiple binding sites on both native and cloned 5-HT3 receptors, and they extend this idea by demonstrating that agonists can modify the interaction of some, but not all, antagonists with the receptor. 相似文献
12.
Karen E. Neil Félix Hernández David A. Kendall Stephen P. H. Alexander 《Journal of neurochemistry》1997,68(6):2610-2617
Abstract: In this report, we have examined the radioligand binding and second messenger signalling characteristics of β-adrenoceptors in the guinea-pig brain. [125 I]lodocyanopindolol ([125 I]ICYP)-labelled sites in the cerebellum and cerebral cortex were of similar densities ( B max 34 and 24 fmol·mg−1 ) and affinities ( K D 20 and 55 p M ), respectively. Analysis of competition for [125 I]ICYP binding in the cerebellum was compatible with the presence of a β2 -adrenoceptor. In this tissue, isoprenaline evoked a cyclic AMP stimulation, and also potentiated cyclic GMP accumulations evoked in the presence of a nitric oxide donor, consistent with mediation via a β2 -adrenoceptor. The [125 I]ICYP binding profile in the cerebral cortex did not comply with those previously described for β-adrenoceptor subtypes, and isoprenaline failed to alter significantly cyclic AMP accumulation in the cerebral cortex, hippocampus, or neostriatum, even in the presence of forskolin or a phosphodiesterase inhibitor. Isoprenaline was also without effect on cyclic GMP accumulation or phosphoinositide turnover in the cerebral cortex. These results suggest that the guinea-pig cerebellum expresses a functional β2 -adrenoceptor coupled to cyclic AMP generation, and potentiation of cyclic GMP accumulation. However, the guinea-pig cerebral cortex displays binding sites that exhibit β-adrenoceptor-like pharmacology but fail to show functional coupling to cyclic AMP, cyclic GMP, or phosphoinositide signalling systems. 相似文献
13.
Ilse Van den Wyngaert †Walter Gommeren Peter Verhasselt †Mirek Jurzak †Josée Leysen Walter Luyten Eckhard Bender 《Journal of neurochemistry》1997,69(5):1810-1819
Abstract: Using a combination of library screening and nested PCR based on a partial human serotonin 5-HT4 receptor sequence, we have cloned the complete coding region for a human 5-HT4 receptor. The sequence shows extensive similarity to the published porcine 5-HT4A and rat 5-HT4L receptor cDNA; however, in comparison with the latter, we find an open reading frame corresponding to only 388 amino acids instead of 406 amino acids. This difference is due to a frame shift caused by an additional cytosine found in the human sequence after position 1,154. Moreover, we also found the same additional cytosine in the rat 5-HT4 sequence. We confirmed the occurrence of the sequence by examining this part of the sequence in genomic DNA of 10 human volunteers and in rat genomic DNA. Based on a part of the genomic 5-HT4 receptor sequence that was identified in the cloning process, there seem to be at least two possible splice sites in the coding region of the gene. The human 5-HT4 receptor, transiently expressed in COS-7 cells, showed radioligand binding properties similar to 5-HT4 receptors in guinea pig striatal tissue. [3 H]GR 113808 revealed K D values of 0.15 ± 0.01 n M for the human receptor and 0.3 ± 0.1 n M in the guinea pig tissue. Binding constants were determined for four investigated 5-HT4 antagonists and three agonists, and appropriate binding inhibition constants were found in each case. Stimulation of transfected COS-7 cells with 5-HT4 -specific agonists caused an increase in cyclic AMP levels. 相似文献
14.
Abstract— [125 I]Diiodo α-bungarotoxin ([125 I]2 BuTx) and [3 H]quinuclidinylbenzilate ([3 H]QNB) binding sites were measured in post-nuclear membrane fractions prepared from whole brains or brain regions of several species. Species studied included Drosophila melanogaster (fruit fly), Torpedo californiea (electric ray), Carassius auratus (goldfish), Ram pipiens (grass frog), Kana cutesheiana (bullfrog), Rattus norvegicus (rat, Sprague-Dawley), Mus muscalus (mouse, Swiss random, C58/J, LG/J), Oryctolagus cuniculus (rabbit, New Zealand Whitc), and Bos (cow). Acetyl-CoA: choline O -acetyltransferase (EC 2.3.1.6) levels were also determined in the post nuclear supernatants and correlated with the number of binding sites.
All species and regions except Drosophila had 16–150 fold more [3 H]QNB binding sites than [125 I]2 BuTx binding sites. Brain regions with the highest levels of [125 I]2 BuTx binding were Drosophila heads (300 fmol/mg), goldfish optic tectum (80fmol/mg), and rat and mouse hippocampus (3040 fmol/mg). The highest levels of [3 H]QNB binding were seen in rat and mouse caudate (1.3–1.6 pmol/mg). Lowest levels of [3 H]QNB and [125 I]2 BuTx binding were seen in cerebellum. The utility of [125 I]2 BuTx and [3 H]QNB binding as quantitative measures of nicotinic and muscarinic acetylcholine receptors in CNS is discussed. 相似文献
All species and regions except Drosophila had 16–150 fold more [
15.
Philippe De Deurwaerdère Marie L'hirondel Norbert Bonhomme Guillaume Lucas André Cheramy Umberto Spampinato 《Journal of neurochemistry》1997,68(1):195-203
Abstract: Serotonin (5-HT) applied at 1, 3, and 10 µ M into the striatum of halothane-anesthetized rats by in vivo microdialysis enhanced dopamine (DA) outflow up to 173, 283, and 584% of baseline values, respectively. The 5-HT effect was partially reduced by 1 or 10 µ M GR 125,487, a 5-HT4 antagonist, and by 100 µ M DAU 6285, a 5-HT3/4 antagonist, whereas the 5-HT1/2/6 antagonist methiothepin (50 µ M ) was ineffective. In the presence of tetrodotoxin the effect of 1 µ M 5-HT was not affected by 5-HT4 antagonists. In addition, tetrodotoxin abolished the increase in DA release induced by the 5-HT4 agonist ( S )-zacopride (100 µ M ). In striatal synaptosomes, 1 and 10 µ M 5-HT increased the outflow of newly synthesized [3 H]DA up to 163 and 635% of control values, respectively. The 5-HT4 agonists BIMU 8 and ( S )-zacopride (1 and 10 µ M ) failed to modify [3 H]DA outflow, whereas 5-methoxytryptamine (5-MeOT) at 10 µ M increased it (62%). In prelabeled [3 H]DA synaptosomes, 1 µ M 5-HT, but not ( S )-zacopride (1 and 10 µ M ), increased [3 H]DA outflow. DAU 6285 (10 µ M ) failed to modify the enhancement of newly synthesized [3 H]DA outflow induced by 5-MeOT or 5-HT (1 µ M ), whereas the effect of 5-HT was reduced to the same extent by the DA reuptake inhibitor nomifensine (1 µ M ) alone or in the presence of DAU 6285. These results show that striatal 5-HT4 receptors are involved in the 5-HT-induced enhancement of striatal DA release in vivo and that they are not located on striatal DA terminals. 相似文献
16.
Abstract: Melatonin and 5-methoxytryptamine inhibited forskolin-stimulated cyclic AMP formation in cultured neural cells prepared from embryonic chick retina. Both methoxyindoles exhibited similar potency and efficacy, with EC50 values of 0.8 n M for melatonin and 7.2 n M for 5-methoxytryptamine. Inhibition of cyclic AMP formation by 5-methoxytryptamine or melatonin was prevented by pretreatment with pertussis toxin. Pretreatment of cultures with 5-methoxytryptamine for 24 h reduced the subsequent inhibitory cyclic AMP response to 5-methoxytryptamine but not that to 2-iodomelatonin. Putative melatonin receptors on cultured retinal cells were labeled with 2-[125 I]iodomelatonin. Melatonin displaced specific 2-[125 I]iodomelatonin with a K i value (0.8 n M ) similar to the EC50 for inhibition of cyclic AMP formation. In contrast, 5-methoxytryptamine only inhibited 2-[125 I]iodomelatonin binding at very high concentrations ( K i = 650 n M ). Pretreating cultured cells for 24 h with 2-iodomelatonin or melatonin, but not with 5-methoxytryptamine, reduced subsequent 2-[125 I]iodomelatonin binding. Thus, 5-methoxytryptamine appears to inhibit forskolin-stimulated cyclic AMP formation at a site distinct from the 2-iodomelatonin binding site. 相似文献
17.
Virginia A. Boundy Robert R. Luedtke Perry B. Molinoff 《Journal of neurochemistry》1993,60(6):2181-2191
Abstract: Portions of the cDNA encoding the third intracellular loop (i3 loop) of the long and short isoforms of the rat D2 dopamine receptor were subcloned into the vector pNMHUBpoly and expressed in Escherichia coli as fusion proteins. The fusion proteins were gel-purified and used to immunize rabbits for the production of polyclonal anti-receptor antisera. The anti-fusion protein antisera recognized synthetic peptides corresponding to segments of the i3 loops of D2 dopamine receptors in a solid-phase radioimmunoassay. Antisera were tested in an immunoprecipitation assay using the reversible D2 antagonist [125 I]NCQ 298 and digitonin-solubilized extracts of canine and rat caudate. [125 I]-NCQ 298 bound reversibly and with high affinity (KD = 0.14 n M ) to receptors in solubilized extracts enriched by chromatography on heparin-agarose. The anti-UBI-D2i3L and anti-UBI-D2i3s antisera were able to immunoprecipitate quantitatively D2 dopamine receptors labeled with [125 I]NCQ 298 from solubilized rat caudate. The antibodies were tested for their ability to affect the coupling of D2 dopamine receptors to GTP-binding proteins in digitonin-solubilized rat caudate. Both anti-UBI-D2i3L and anti-UBI-D2i3s antisera were able to inhibit the high-affinity binding of the agonist N -propylnorapomorphine to digitonin-solubilized rat caudate. These findings indicate that the i3 loop of the D2 dopamine receptor is an important determinant for coupling of the G protein. 相似文献
18.
D. A. Clemett M. I. Cockett C. A. Marsden K. C. F. Fone 《Journal of neurochemistry》1998,71(3):1271-1279
Abstract: The effect of a 5-hydroxytryptamine7 (5-HT7 ) receptor-directed antisense oligonucleotide on rat behaviour and neuroendocrine function was investigated. Six days of intracerebroventricular 5-HT7 antisense oligonucleotide treatment significantly reduced [3 H]5-HT binding to hypothalamic 5-HT7 receptors, whereas cortical 5-HT2C density remained unchanged. In rats on a food-restricted diet, both antisense and mismatch oligonucleotides reduced food intake and body weight compared with that in vehicle-treated controls by day 4 of administration. 5-HT7 antisense oligonucleotide administration did not affect exploratory or locomotor activity in photocell activity monitors on day 4 or elevated plus-maze behaviour on day 6 of intracerebroventricular treatment. 5-HT7 antisense oligonucleotide did not affect plasma corticosterone or prolactin levels or 5-HT turnover in either 5-HT cell body or terminal areas. These data demonstrate that intracerebroventricular 5-HT7 antisense oligonucleotide administration selectively reduced rat hypothalamic 5-HT7 receptor density without affecting any of the biochemical or behavioural measures. The results suggest that this antisense protocol could be a valuable tool to investigate central 5-HT7 receptor functions, and that this receptor is not critical for the control of neuroendocrine function or food intake. 相似文献
19.
Abstract : Single treatment with the serotonin (5-hydroxytryptamine) 5-HT1A receptor agonists 8-hydroxy-2-(di- n -propylamino)tetralin (8-OH-DPAT) and alnespirone (S-20499) reduces the extracellular 5-HT concentration (5-HText ) in the rat midbrain and forebrain. Given the therapeutic potential of selective 5-HT1A agonists in the treatment of affective disorders, we have examined the changes in 5-HT1A receptors induced by 2-week minipump administration of alnespirone (0.3 and 3 mg/kg/day) and 8-OH-DPAT (0.1 and 0.3 mg/kg/day). The treatment with alnespirone did not modify baseline 5-HText but significantly attenuated the ability of 0.3 mg/kg s.c. alnespirone to reduce 5-HText in the dorsal raphe nucleus (DRN) and frontal cortex. In contrast, the ability of 8-OH-DPAT (0.025 and 0.1 mg/kg s.c.) to reduce 5-HText in both areas was unchanged by 8-OH-DPAT pretreatment. Autoradiographic analysis revealed a significant reduction of [3 H]8-OH-DPAT and [3 H]WAY-100635 {3 H-labeled N -[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]- N -(2-pyridyl)cyclohexanecarboxamide · 3HCl} binding to somatodendritic 5-HT1A receptors (but not to postsynaptic 5-HT1A receptors) of rats pretreated with alnespirone but not with 8-OH-DPAT. In situ hybridization analysis revealed no change of the density of the mRNA encoding the 5-HT1A receptors in the DRN after either treatment. These data indicate that continuous treatment for 2 weeks with alnespirone, but not with 8-OH-DPAT, causes a functional desensitization of somatodendritic 5-HT1A receptors controlling 5-HT release in the DRN and frontal cortex. 相似文献
20.
A. Cagnotto D. Crespi L. Mancini C. Manzoni M. L. Presti M. Gariboldi A. Vezzani T. Mennini 《Journal of neurochemistry》1998,70(2):850-857
Abstract: We examined the effect of kindling on serotonergic neurotransmission in the hippocampus by measuring serotonin (5-HT) release and uptake in hippocampal synaptosomes and 5-HT1A and 5-HT4 receptor subtypes during and at different times after electrical kindling of the dentate gyrus. Using quantitative receptor autoradiography, we found that binding of 8-[3 H]hydroxy-2-(di- n -propylamino)tetralin ([3 H]8-OH-DPAT) to 5-HT1A receptors was selectively increased by 20% on average ( p < 0.05) in the dentate gyrus of the stimulated and contralateral hippocampus 2 days after stage 2 (stereotypes and occasional retraction of a forelimb) and by 100% on average ( p < 0.05) 1 week after stage 5 (tonic-clonic seizures) compared with sham-stimulated rats. A 20% increase ( p < 0.05) was observed 1 month after the last generalized seizure. No changes were found after a single afterdischarge. 5-HT4 receptors, which colocalize with 5-HT1A receptors on hippocampal neurons, were not modified in kindled tissue. [3 H]5-HT uptake and its release as well as the 5-HT1B autoreceptor function did not differ from shams in hippocampal synaptosomes at stages 2 and 5. Systemic administration of 100 and 1,000 µg kg−1 8-OH-DPAT or 1,000 µg kg−1 WAY-100,635, 30 min before each electrical stimulation, did not significantly alter kindling progression or the occurrence of stage 5 seizures in fully kindled rats. The changes in 5-HT1A receptor density in the dentate gyrus are part of the plastic modifications occurring during kindling and may contribute to modulating tissue hyperexcitability. 相似文献