[Show abstract][Hide abstract] ABSTRACT: There is considerable evidence of altered glutamatergic signalling in schizophrenia and a polymorphic variant of the GRIK3 glutamate receptor gene on 1p34-33 has previously been associated to this psychotic disorder. We therefore conducted a systematic association study with 30 HapMap-selected tagging SNPs across GRIK3 in three independent samples of Scandinavian origin from the Scandinavian Collaboration of Psychiatric Etiology (SCOPE), including a total of 839 cases with schizophrenia spectrum and 1473 healthy controls. Four markers (rs6671364, rs17461259, rs472188, and rs535620) attained nominally significant P-values in both the genotypic (0.002, 0.02, 0.03, and 0.05, respectively) and allelic (0.001, 0.006, 0.03, and 0.02, respectively) association tests for the combined sample, and 2 additional markers (rs481047and rs1160751) displayed significance for the genotype (P-values: 0.03 and 0.04). Several haplotypes, that all included at least one of the four SNPs implicated by the single marker analysis, remained significant after adjustment for multiple testing using permutations with 10,000 shuffles. In addition we observed an association for two of the four significant GRIK3 markers (rs472188 and rs535620) to scores for negative symptoms on the PANSS scale. The present results, although not robust, support the importance of more extensive investigations of GRIK3, given its potential role in mediating risk for schizophrenia.
Schizophrenia Research 12/2008; 107(2-3):242-8. · 4.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Schizophrenia is a highly heritable complex psychiatric disorder with an underlying pathophysiology that is still not well understood. Metaanalyses of schizophrenia linkage studies indicate numerous but rather large disease-associated genomic regions, whereas accumulating gene- and protein expression studies have indicated an equally large set of candidate genes that only partially overlap linkage genes. A thorough assessment, beyond the resolution of current GWA studies, of the disease risk conferred by the numerous schizophrenia candidate genes is a daunting and presently not feasible task. We undertook these challenges by using an established clinical paradigm, the estrogen hypothesis of schizophrenia, as the criterion to select candidates among the numerous genes experimentally implicated in schizophrenia. Bioinformatic tools were used to build and priorities the signaling networks implicated by the candidate genes resulting from the estrogen selection. We identified ten candidate genes using this approach that are all active in glucose metabolism and particularly in the glycolysis. Thus, we tested the hypothesis that variants of the glycolytic genes are associated with schizophrenia or at least with gender-associated aspects of the illness.
We genotyped 185 SNPs in three independent case-control samples of Scandinavian origin (a total of 765 patients and 1274 control subjects). Variants of the mitogen-activated protein kinase 14 gene (MAPK14) and the phosphoenolpyruvate carboxykinase 1 (PCK1) and fructose-1,6-biphosphatase (FBP1) were nominal significantly associated with schizophrenia, and several haplotypes within enolase 2 gene (ENO2) consist of the same SNP allele having elevated risk of schizophrenia. Importantly, we find no evidence of stratification due to nationality or gender.
Several gene variants in the Glycolysis were associated with schizophrenia in three independent samples. However, the findings are weak and not resistant to correction for multiple testing, which may indicate that they are either spurious or may relate to a particular subtype or aspect of the illness.
BMC Medical Genetics 02/2008; 9:39. · 2.54 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Two benzodiazepine analogues, [3H]flumazenil and [3H]sarmazenil, were used to study the GABAA/benzodiazepine receptor complex in human post-mortem brain using in vitro receptor assays on homogenates and whole hemisphere autoradiography. Both radioligands bound in a saturable manner to single binding sites in the tissue preparations from any brain region. The highest levels of binding were found in the cortical regions and in cortex cerebelli. Both [3H]flumazenil and [3H]sarmazenil were excellent radioligands for autoradiography with high binding in cerebral and cerebellar cortex with no or very low binding in areas with white matter. The addition of a high concentration of flumazenil or clonazepam did not inhibit the binding of [3H]sarmazenil to granule cells in the cerebellum while the binding of [3H]flumazenil was abolished completely in all regions. The results show that with the two different radioligands, one an antagonist and one a partial inverse agonist, the binding pattern to GABAA/benzodiazepine receptor complex is approximately similar in most brain regions. The additional binding seen in the cerebellum with [3H]sarmazenil is suggested to be due to binding to an α6-containing complex.
Human Psychopharmacology Clinical and Experimental 10/2004; 7(6):367 - 377. · 2.10 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Tc(III) and Re(III) complexes [M(NS(3))(CNR)] (M = Re, 99mTc, NS(3) = 2,2',2"-nitrilotris(ethanethiol), CNR = functionalized isocyanide bearing a derivative of WAY 100635) have been synthesized and characterized. Re was used as Tc surrogate for chemical characterization and in vitro receptor-binding studies. For two representatives subnanomolar affinities for the 5-HT(1A) as well as for the alpha1-adrenergic receptor were reached. Biodistribution studies in rats of the 99mTc complexes showed brain uptakes between 0.3 and 0.5% ID/organ (5 min p.i.). In vitro autoradiography of one 99mTc representative in sections of post mortem human brain indicate its accumulation in 5-HT(1A) receptor-rich brain regions. However, addition of the specific 5-HT(1A) receptor agonist 8-OH-DPAT as well as the alpha1-adrenoceptor antagonist prazosin could not substantially block this tracer accumulation. A preliminary SPET study in a monkey showed negligible brain uptake.
Nuclear Medicine and Biology 06/2002; 29(4):389-98. · 2.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This paper reports the synthesis, biological evaluation, in vitro and ex vivo autoradiography of the first Tc-99m ligand with subnanomolar affinity for the 5-HT(1A) receptor and a remarkably high affinity for the alpha1-adrenergic receptor. The neutral "3+1" mixed-ligand complex combines 4-(6-mercaptohexyl)-1-(2-methoxyphenyl)piperazine as monodentate and 3-(N-methyl)azapentane-1,5-dithiol as tridentate unit with oxotechnetium(V). The analogous rhenium complex was synthesized for complete structural characterization and used in receptor binding assays. In competition experiments both complexes display subnanomolar affinity for the 5-HT(1A) receptor (IC(50)0.24 nM for Re, 0.13 nM for Tc) but also very high affinities for the alpha1-adrenergic receptor (IC(50) 0.05 nM for Re, 0.03 nM for Tc). Biodistribution studies show a brain uptake in rat of 0.22% ID five minutes post injection. In vitro autoradiographic studies in rat brain and postmortem human brain indicate accumulation of the Tc-99m complex in brain areas which are rich in 5-HT(1A) receptors or in alpha1-adrenergic receptors. This in vitro enrichment can be blocked respectively by the 5-HT(1A) receptor agonist 8-OH-DPAT or by prazosin hydrochloride, an alpha1-adrenergic receptor antagonist. Ex vivo autoradiographic studies in rats show a slight accumulation of the Tc-99m complex in 5-HT(1A) receptor-rich areas of the brain, which could not be blocked, as well as in regions rich in alpha1-adrenergic receptors, which could be blocked by prazosin hydrochloride.
Nuclear Medicine and Biology 06/2002; 29(4):375-87. · 2.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: [35S]GTPgammaS binding autoradiography is a novel method to study the distribution and function of neurotransmitter receptors in tissue sections. This technique unifies the advantages of receptor-autoradiography and [35S]GTPgammaS binding, providing anatomical and functional information at the same time. Due to these two main features, it can also be called 'functional autoradiography'. [35S]GTPgammaS binding has long been used to study the first step of the intracellular signaling pathway, but until the mid 1990s it has only been performed on cell membrane extracts. Functional autoradiography evolved from this biochemical assay and ligand autoradiography, and is based on the increase in guanine nucleotide exchange at G-proteins upon agonist stimulation. With the technique, activation of G-protein-coupled receptors upon agonist binding can be detected, and, at the same time, the location of activated receptors can also be visualized. Thus only those presumably active G-protein-coupled receptors are visualized that can be involved in signal transduction. In the past 5 years the technique has become more and more frequently used in neuroscience, and it has been adapted to several receptors in different species, including also the human brain. [35S]GTPgammaS binding autoradiography can be used to describe the distribution of G-protein-coupled receptors. Some inferences on their coupling efficiency can also be drawn. Besides the localization of ligand binding sites, it provides information on the action of the ligand on the receptor: agonists, antagonists, and inverse agonists can clearly be distinguished. Moreover, [35S]GTPgammaS binding autoradiography can successfully be combined with other in vitro assays, like receptor autoradiography, in situ hybridization histochemistry, or even with biochemical and electrophysiological experiments. This review presents an overview on the history and the development of this technique. Its main advantages and limitations are summarized, together with a few basic technical questions. A number of experiments performed with [35S]GTPgammaS binding autoradiography so far, and some possible applications for the future, are also reviewed.
Brain Research Reviews 01/2002; 38(1-2):149-64. · 7.82 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The main objective ofthe study was to evaluate with autoradiographic technique whether or not [11C]vinpocetine, a compound widely used in the prevention and treatment of cerebrovascular diseases (Cavinton, Gedeon Richter Ltd., Budapest), binds to specific sites in the human brain in post mortem human brain sections. Binding was assessed under four conditions: the incubation was performed using Tris-HCl buffer with or without the addition of salts (0.1% (weight/vol) ascorbic acid, 120 mM NaCl, 5 mM KCl, 2 mM CaCl2 and 1 mM MgCl2), with or without the addition of excess (10 microM) unlabelled vinpocetine. Measurements on digitized autoradiograms indicated that [11C]vinpocetine labelled all grey matter areas in the human brain to a similar extent and no significantly heterogeneous binding could be demonstrated among cortical or subcortical regions. The addition of excess unlabelled vinpocetine lowered the binding slightly in all regions. Although these results indicate that [11C]vinpocetine does not bind to human brain transmitter receptors or transporters with a high affinity (Ki < 10 nM), it cannot be ruled out that the compound binds to receptors and/or transporters with lower affinity.
[Show abstract][Hide abstract] ABSTRACT: The distribution of 5-HT(1B) and 5-HT(1D) receptors in the human post mortem brain was examined using whole hemisphere autoradiography and the radioligand [(3)H]GR 125743. [(3)H]GR 125743 binding was highest in the substantia nigra and the globus pallidus. Lower levels were detected in the striatum, with the highest densities in the ventromedial parts. In the amygdala, the hippocampus, the septal region and the hypothalamus, lower [(3)H]GR 125743 binding was observed, reflecting low densities of 5-HT(1B/1D) receptors. In the cerebral cortex, binding was similar in most regions, although restricted parts of the medial occipital cortex were markedly more densely labeled. Binding densities were very low in the cerebellar cortex and in the thalamus. Two methods were used to distinguish between the two receptor subtypes, the first using ketanserin to block 5-HT(1D) receptors and the second using SB 224289 to inhibit 5-HT(1B) receptor binding. The autoradiograms indicated that in the human brain, the 5-HT(1B) receptor is much more abundant than the 5-HT(1D) receptor, which seemed to occur only in low amounts mainly in the ventral pallidum. Although [(3)H]GR 125743 is a suitable radioligand to examine the distribution of 5-HT(1B) receptors in the human brain in vitro, the selectivities of ketanserin and SB 224289 are not sufficiently high to give definite evidence for the occurrence of the 5-HT(1D) receptor in the human brain.
Brain Research 11/2001; 915(1):47-57. · 2.88 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Dopaminergic mechanisms are involved in the positive reinforcing and addicting effects of alcohol. Positron emission tomography (PET) and single photon emission tomography (SPET) studies have indicated alterations in striatal dopamine transporters (DAT) and in presynaptic dopamine (DA) function in alcoholics, although also contradictory results have been reported. Normal variations in blood flow, metabolism, and receptor densities are apparently important to brain function. Such variations are known to decrease during pathophysiological processes, such as epilepsy, whereas normal receptor distributions are broadly heterogenous. We evaluated the densities and heterogeneities of striatal DAT in 8 adult-onset, Cloninger type I alcoholics and 10 controls using [125I]N-(3-iodoprop-2E-enyl)-2beta-carbomethoxy-3beta- (4'-methylphenyl)nortropane ([125I]PE2I) as a ligand for human postmortem whole hemisphere autoradiography, which provided high resolution images of the brain when compared with in vivo PET and SPET. The mean density and heterogeneity of DAT were markedly lower in the alcoholics. A significant linear correlation existed between DAT density and heterogeneity, as well as between DAT densities in the nucleus accumbens and in the dorsal striatum (caudate and putamen) in alcoholics, but not consistently in controls. The observed low DAT density and heterogeneity in the dorsal striatum suggest that type 1 alcoholics may have a dysfunctional DA system. These data indicate that human whole hemisphere autoradiography with the analysis of binding heterogeneity may be a relevant tool to measure pathological processes in the brain.
[Show abstract][Hide abstract] ABSTRACT: Alcohol acts through mechanisms involving the brain neurotransmitter dopamine (DA) with the nucleus accumbens as the key zone for mediating these effects. We evaluated the densities of DA D(2)/D(3) receptors and transporters in the nucleus accumbens and amygdala of post-mortem human brains by using [(125)l]epidepride and [(125)I]PE2I as radioligands in whole hemispheric autoradiography of Cloninger type 1 and 2 alcoholics and healthy controls. When compared with controls, the mean binding of [(125)I]epidepride to DA D(2)/D(3) receptors was 20% lower in the nucleus accumbens and 41% lower in the amygdala, and [(125)I]PE2I binding to DA transporters in the nucleus accumbens was 39% lower in type 1 alcoholics. These data indicate that dopaminergic functions in these limbic areas may be impaired among type 1 alcoholics, due to the substantially lower number of receptor sites. Our results suggest that such a reduction may result in the chronic overuse of alcohol as an attempt to stimulate DA function.