Differential expression of glycine receptor subunits in the rat basolateral and central amygdala

The amygdalar complex is a limbic structure that plays a key role in emotional processing and fear conditioning. Although inhibitory transmission in the amygdala is predominately GABA-ergic, neurons of the amygdala are also known to express glycine receptors. The subtype and function of these glycine receptors within the synaptic circuits of the amygdala are unknown. In this study, we have investigated the relative expression of the four major glycine receptor subunits (α1–3 and β) in the rat basolateral (BLA) and central amygdala (CeA), using real-time PCR and protein biochemistry. We demonstrate that α1, α2, α3, and β subunits are all expressed in the BLA and CeA with α2 being the predominant α-subunit in both nuclei. Electrophysiological recordings from BLA and CeA neurons in acute brain slices indicated that differences in relative expression of these subunits were correlated with the pharmacological properties of native glycine receptors expressed on these neurons. We conclude that glycine receptors assembled in BLA neurons are largely α1β-containing heteromultimers whereas receptors assembled in neurons of the central amygdala are primarily α2β-, α3β- or α1β-containing heteromultimers, with a minor component of α2 or α3 homomeric receptors also expressed.     

Role of Integrin Receptors for Fibronectin,Collagen and Laminin in the Regulation of Ovarian Carcinoma Functions in Response to a Matrix Microenvironment

Integrins play an important role in cellular matrix interactions requisite for cancer cell adhesion, growth, migration and invasion. In this study, we have investigated the expression of integrin subunits α3, α6, αv and β1 in normal ovaries, benign ovarian tumors and ovarian carcinomas of different pathological grades. The expression of these integrins in ovarian cancer cell lines was also investigated, and their role in sustaining proliferation, adhesion, migration and invasion in cohort with the activation of signaling pathways in response to extracellular matrices (ECM) was evaluated. We demonstrate a differential expression pattern of α3, α6, αv and β1 integrin subunits in ovarian carcinomas compared to normal ovaries and benign ovarian tumors. Ovarian cancer cell lines (Hey, Ovcar3 and Peo.36) demonstrated significantly high expression of α3, α6, αv and β1 integrin subunits. A significant increase in proliferation and adhesion (P<0.05) in response to collagen 1 (Coll) and laminin (LM), ligands for integrin receptor α3β1 and α6β1 was observed in ovarian cancer cell lines. On the other hand, fibronectin (FN), a receptor for αvβ1 integrin, increased proliferation in all ovarian cancer cell lines studied but only enhanced adhesion in Hey cell line (P<0.05). Neutralizing antibodies against α3, α6, αv and β1 integrin subunits inhibited ECM-induced proliferation, but increased adhesion to ECM was inhibited by β1 integrin subunit antibody. No suppression of Coll, LM and FN-induced (Hey cells only) adhesion was observed in the presence of α3 or αv subunit antibodies but LM-induced adhesion was inhibited by blocking α6 subunit functions. LM, FN and Coll enhanced chemotactic migration in Hey cells, but direct invasion across ECM was observed only in the presence of LM and Coll. Blocking antibodies against α3, α6 and β1 integrin subunits inhibited both chemotactic migration and invasion of Hey cells in response to respective ECM. Adhesion of ovarian cancer cells to FN, Coll and LM activated Ras, Erk and Akt pathways. Neutralizing αv and β1 functions did not inhibit FN-induced activation of Ras and Erk pathways but inhibited the Akt pathway. On the other hand, antibodies against α6 and β1 subunits, but not α3 subunit, inhibited LM-induced activation of Ras but did not inhibit the downstream Akt pathway. Neutralizing β1 subunit function however, inhibited LM-induced Erk activation. Coll-induced activation of Ras, Erk and Akt pathways was inhibited by α3 and β1 integrin subunit antibodies. These results indicate that α3β1, αvβ1 and α6β1 integrin mediate proliferation, adhesion, migration and invasion of ovarian cancer cells in response to ECM and targeting these integrins to modulate integrin–ECM interactions in tumor cells may be a promising tool to reduce the dissemination of ovarian carcinoma in vivo.     

Detection of inhibin α and βA subunits (inhibin A, B, activin A,AB) in the human pituitary gland and in pituitary adenomas by immunohistochemistry and nonradioisotopicin situ hybridization

Inhibin and activin are gonadal hormones produced in human ovaries. They are known to act on anterior pituitary cells to regulate the synthesis and secretion of follicle-stimulating hormone (FSH). The purpose of the present study was to determine the localization of inhibin and activin subunits α and βA as endocrine markers in the human normal pituitary gland and pituitary adenomas, using immunohistochemistry andin situ hybridization (ISH) methods. Pituitary tissues from surgical and autopsy materials were fixed in 10% formalin and embedded in paraffin. Five normal pituitary glands and 79 pituitary adenomas were immunostained with the avidin-biotin peroxidase complex (ABC) method using polyclonal antibodies against inhibin and activin subunits α and βA. The other antibodies against anterior pituitary hormones used in this study were as follows: antigrowth hormone (anti-GH), antiprolactin (anti-PRL), antiadrenocorticotropic hormone (anti-ACTH), anti-FSHβ, antilutenizing hormone (anti-LH) β, antithyroid-stimulating hormone (anti-TSH) β, and antiglycoprotein α-subunit (anti-α-SU). We analyzed gene expressions of subunits α and βA by nonradioisotopic ISH in pituitary adenomas. In the normal human pituitary glands, inhibin and activin subunits α and βA immunoreactivities were found diffusely in the cytoplasm of anterior pituitary cells. The percentage of subunit α-immunopositive cells was 40% of the anterior pituitary cells. Subunit βA immunoreactivities were observed in about 15% of the anterior pituitary cells. By the double-staining method, subunit α immunoreactivity was detected in all types of anterior pituitary cells, and it was colocalized most frequently with GH and α-SU-positive cells. Subunit βA immunoreactivity was colocalized predominantly with PRL, FSH-β, LH-β, and α-SU. Among the 79 adenomas, 75 cases (94.9%) were positive for subunit α, and 50 cases (63.3%) were positive for subunit βA. Subunit βA was positive in tumor cells with the following incidences: GH adenomas, 3 of 14 (21.4%); PRL adenomas, 5 of 8 (62.5%); ACTH adenomas, 6 of 6 (100%); TSH adenomas, 7 of 7 (100%); nonfunctioning adenomas, 29 of 44 (65.9%), including gonadotropin-positive, 16 of 22 (80.0%). The ISH signals for subunits α and βA were strongly expressed in gonadotropin-positive adenomas among the nonfunctioning adenomas. The mRNA signals were low and infrequent in the GH-producing adenomas. Inhibin and activin subunit α localization did not demonstrate cell-type specificity in pituitary adenomas. In contrast, subunit βA demonstrated predominant positivity in the functioning pituitary adenomas (ACTH- and TSH-secreting) and nonfunctioning adenomas (including gonadotropin-positive adenomas). The present results suggest that the functional role of inhibin and activin in the differentiation of cells in normal human pituitary glands and adenomas is present in subunit βA.     

Determination of the architecture of ionotropic receptors using AFM imaging

Fast neurotransmission in the nervous system is mediated by ionotropic receptors, all of which contain several subunits surrounding an integral ion channel. There are three major families of ionotropic receptors: the ‘Cys-loop’ receptors (including the nicotinic receptor for acetylcholine, the 5-HT₃ receptor, the GABA_A receptor and the glycine receptor), the glutamate receptors (including the α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid, kainate and N-methyl-d-aspartic acid receptors) and the P2X receptors for adenosine triphosphate. These receptors are often built from multiple types of subunit, raising the question of the stoichiometry and subunit arrangement within the receptors. This question is of therapeutic significance because in some cases drug-binding sites are located at subunit–subunit interfaces. In this paper, we describe a general method, based on atomic force microscopy imaging, to solve the architecture of multi-subunit proteins, such as the ionotropic receptors. Specific epitope tags are engineered onto each receptor subunit. The subunits are then expressed exogenously in cultured cells, and the receptors are isolated from detergent extracts of membrane fractions by affinity chromatography. The receptors are imaged both alone and in complex with anti-epitope antibodies. The size of the imaged particles provides an estimate of the subunit stoichiometry, whereas the geometry of the receptor–antibody complexes produces more detailed information about the receptor architecture. We use an automated, unbiased system to identify receptors and receptor–antibody complexes and to determine the geometry of the complexes. We are also able to determine the orientation of the receptors on the mica substrate, which will allow us to solve the subunit arrangement within receptors, such as the GABA_A receptor, which contain three types of subunits.     

The Content of PPAR,LXR, and RXR and the PPAR DNA-Binding Activity in Macrophages over the Course of Inflammation in Mice

The content of peroxisome proliferation activating proteins PPAR-α and PPAR-γ, liver X receptors (LXR), and retinoid X receptors (RXR) and activity of PPAR-α, PPAR-γ, and PPAR-δ binding to DNA response elements in C57Bl/6 mouse macrophages were studied during different phases of aseptic inflammation, induced by intraperitoneal injection of 50 mg/kg zymosan A. The DNA-binding activities of PPAR-α and PPAR-γ and the levels of PPAR-α, PPAR-γ, LXR, and RXR in peritoneal macrophages dropped on days 1 and 3 after zymosan injection. On days 7 and 14 the DNA-binding activity of PPAR-γ and content of PPAR-γ and LXR-β protein increased in comparison with the control, while the DNA-binding activity and content of PPAR-α in the cells remained low. Recovery of RXR protein content in macrophages was observed only on day 14 after zymosan injection. Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 147, No. 3, pp. 317–321, March, 2009     

Functional blocking of specific integrins inhibit colonic cancer migration

For more effective oncological management of disseminated colorectal cancer, therapies must be devised that target the different individual stages of metastasis development. Recent work showed that integrin subunits α2, α6 and β4 are involved in the colorectal cancer cell extravasation process. By means of Immunocytochemistry and Western blotting, it was shown that all three integrins are expressed not only in human colorectal cancer cells (HT29) but also in rat colonic cancer cells (DHDK12). Using in vivo models and intravital video microscopy techniques, it was shown that functional blocking of these integrin subunits by specific antibodies produced a significant reduction in cancer cell extravasation and migration. In conclusion, integrin subunits α2, α6 and β4 are expressed in unrelated colorectal cancer cell strains and appear to play a key role in cancer cell migration.     

Expression of integrin subunits correlates with differentiation of epithelial cell lineages in developing human gastric mucosa

Laminins may play important roles in gastric gland development due to the differential localization of their α chains in human fetal fundic (oxyntic) mucosa. To extend this hypothesis, the current investigation was undertaken to compare the anatomical and cellular distribution of epithelial integrin subunits with those of laminin α chains in the human stomach at different ages (8–22 weeks of gestation) using indirect immunofluorescence. In the body, fundus and antrum regions, the β1 and α6 subunits were associated with the entire epithelium at all developmental stages in the same way as laminin chains (α1/α5) detected with 4C7 monoclonal antibody. By contrast, the α3 and β4 subunits of α3β1 and α6β4 integrins together with the laminin α3-chain were concentrated in the surface and foveolus compartments composed of differentiating mucous cells. Most importantly, the α2 integrin subunit was expressed in a rather complex pattern: (1) it was located at the base and at cell-cell boundaries of surface/foveolar epithelium, (2) was specifically repressed in differentiating parietal cells, and (3) its expression increased in maturing glands, where it became concentrated at the basal pole of epithelial cells simultaneously exhibiting a strong reactivity for laminin-2 (α2-chain). Taken altogether, our observations provide new evidence for the implication of different laminins and their receptors in the development of all human gastric epithelial lineages, surface mucous cells or glandular cells. The coordinated expression of α2 and α3 integrin subunits as well as the cellular re-distribution of α2β1 integrin likely represent key events for the differentiation of glandular secretory cell types, especially maturing chief cells responsible for the synthesis/secretion of gastric digestive enzymes in fundic-type glands. Accepted: 26 March 2000     

Characterization of the genomic structure of the human neuronal nicotinic acetylcholine receptor CHRNA5/A3/B4 gene cluster and identification of novel intragenic polymorphisms

Genes coding for the α5, α3, and β4 subunits (CHRNA5, CHRNA3, and CHRNB4) of the neuronal nicotinic acetylcholine receptors (nAChRs) are clustered on chromosome 15q24. Linkage of this chromosomal region to autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE), an idiopathic partial epilepsy, was reported in one family. Moreover, mutations in other neuronal nAChR subunit genes coding for the α4 (CHRNA4) and the β2 (CHRNB2) subunits were associated with ADNFLE. Apart from the exon-intron structure of CHRNA3, the geno-mic organization of this gene cluster was unknown, making comprehensive mutational analyses impossible. The genomic structure of CHRNA5 and CHRNB4 is here reported. Moreover, two hitherto unknown introns were identified within the 3′ untranslated region of CHRNA3, causing a partial tail-to-tail overlap with CHRNA5. Four novel intragenic polymorphisms were identified and characterized in the cluster. Received: May 11, 2001 / Accepted: August 16, 2001     

Role of the interaction between different types of serotonin and α2-adrenergic receptors in the regulation of audiogenic seizures in DBA/2 micereceptors in the regulation of audiogenic seizures in DBA/2 mice

It is shown that the serotonin receptors 5-HT_1c, 5-HT₃, and 5-HT₄ and α₂-adrenergic receptors are involved in the regulation of audiogenic seizures in DBA/2 mice, and that the effects of these serotonin receptors on the duration and magnitude of convulsive activity are the opoosite of those produced by α₂-adrenergic receptors. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 119, N ^o 4, pp. 381–383, April, 1995     

Non-NMDA receptors in frog retina: an immunocytochemical study

Glutamate is one of the main neurotransmitters in the retina. Its effects are mediated by a large number of ionotropic and metabotropic membrane receptors. The distribution of ionotropic AMPA receptor subunits GluR1-4, kainate receptor subunits GluR5-7 and KA2, delta receptors 1-2, as well as the metabotropic receptor mGluR6 were studied in the frog retina. Indirect immunofluorescence was used to localize the different receptor subunits. Results showed that all subunits, with the exception of GluR1 and GluR5, are widely distributed in the retina. They are mainly located in both plexiform layers: the outer (OPL) and the inner one (IPL), where punctate labelling, a sign of synaptic localization, is observed. The metabotropic receptor mGluR6 is localised only in the OPL. The AMPA receptor subunit GluR4 is localised on the glial Müller cells of the retina. The vast majority of the subunits possess specific patterns of labelling that indicate that they are involved with different retinal functions. The significance of the AMPA receptors and involvement of glia in modulation of synaptic transmission are discussed.     

Expression of sex steroid hormone receptors in C cell hyperplasia and medullary thyroid carcinoma

Previous studies have shown that C cells are twice as numerous in male than in female thyroids and that C cell hyperplasia (CCH) is much more frequent in men. These findings suggest regulation involving sex steroid hormones through the expression of sex steroid hormone receptors on C cells. To investigate this hypothesis, we performed an immunohistochemical study of estrogen receptors α (ERα) and β (ERβ), progesterone receptors (PR), and androgen receptors (AR) on specimens from a series of 40 patients operated on for a medullary thyroid carcinoma (MTC; n = 28; female 18, male 10) and/or CCH (n = 19; female 6, male 13). ERβ was the only receptor to be consistently expressed in CCH (100%) and MTC (96.5%), whereas ERα was never expressed. PR and AR were rarely expressed in MTC (7 and 14%, respectively). AR was expressed in half the CCH cases (53%), with a trend to male predominance (61% in men vs 33% in women). Our study is the first to describe ERβ expression in CCH. In addition, our findings suggest that CCH, and possibly MTC, might be influenced by sex steroid hormones, namely, estrogens and androgens, through the expression of ERβ and AR on C cells.     

Chromosome elimination in the interspecific hybrid medaka between <Emphasis Type="Italic">Oryzias latipes</Emphasis> and <Emphasis Type="Italic">O. hubbsi</Emphasis>

An interspecific hybrid medaka (rice fish) between Oryzias latipes and O. hubbsi is embryonically lethal. To gain an insight into the cellular and molecular mechanisms that cause the abnormalities occurring in the hybrid medaka, we investigated the behavior of chromosomes and the expression patterns of proteins responsible for the chromosome behavior. The number of chromosomes in the hybrid embryos gradually decreased to nearly half, since abnormal cell division with lagging chromosomes at anaphase eliminated the chromosomes from the cells. The chromosome lagging occurred at the first cleavage and continued throughout embryogenesis even after the midblastula transition. Fluorescent in-situ hybridization analyses revealed that the chromosomes derived from O. hubbsi are preferentially eliminated in both O. latipes–hubbsi and O. hubbsi–latipes embryos. Whole-mount immunocytochemical analyses using antibodies against α-tubulin, γ-tubulin, inner centromere protein, Cdc20, Mad2, phospho-histone H3 and cohesin subunits (SMC1α, SMC3 and Rad21) showed that the expression patterns of these proteins in the hybrid embryos are similar to those in the wild-type embryos, except for phospho-histone H3. Phospho-histone H3 present on chromosomes at metaphase was lost from normally separated chromosomes at anaphase, whereas it still existed on lagging chromosomes at anaphase, indicating that the lagging chromosomes remain in the metaphase state even when the cell has proceeded to the anaphase state. On the basis of these findings, we discuss the cellular and molecular mechanisms of chromosome elimination in the hybrid medaka.     

Role of ATP as a sympathetic nervous system transmitter in the smoothing of rapid arterial pressure changes

Arterial pressure lability and its variations were examined in unrestrained rats following selective elimination of adrenergic or purinergic sympathetic influences on the circulatory system. Both the α₁-andrenoceptor blocker prazosin and the nonselective α-adrenoceptor blocker phentolamine lowered the arterial pressure without affecting its lability. When P_2x purine receptors were desensitized with α,β-methyleneATP, the resulting pronounced hypotension was accompanied by a two-fold increase in the lability of mean arterial pressure. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 120, N^no 11, pp. 461–464, November, 1995 Presented by I. P. Ashmarin, Member of the Russian Academy of Medical Sciences     

Expression of the 67 kDa laminin receptor and the α6 integrin subunit in serous ovarian carcinoma

The aim of this study was to analyze the expression of two laminin receptors, the 67kDa laminin receptor (LBP) precursor and the α6 integrin subunit, in effusions and solid tumors of patients diagnosed with serous ovarian carcinoma and to evaluate their predictive role. Eighty-eight effusions and one hundred sixteen primary (= forty-one) and metastatic (= seventy-five) ovarian carcinomas were evaluated for expression of the above-mentioned mRNAs using in situ hybridization (ISH). LBP protein expression was studied in 24 effusions and 43 solid tumors using immunohistochemistry (IHC). α6 integrin subunit protein expression was studied in 27 effusions using flow cytometry (FCM). Expression of LBP mRNA was frequently detected in both carcinoma (92 of 116 cases, 79%) and stromal (79 of 116 cases, 68%) cells in solid tumors. Expression was still higher in cancer cells in effusions (85 of 88 specimens, 96%). In contrast, α6 integrin subunit was less frequently detected in both solid tumors (33 of 116; 28% in carcinoma cells, 23 of 116; 20% in stromal cells) and effusions (36 of 88; 41%). LBP protein expression was found in 19 of 24 (79%) effusions and 40 of 43 (93%) solid tumors, and was higher in effusions of patients who received chemotherapy prior to tapping (P = 0.024). FCM showed protein expression of the α6 integrin subunit in 17 of 27 (63%) effusions. Expression of the α6 integrin subunit mRNA in tumor cells of solid lesions was significantly lower in solid tumors of FIGO stage-IV patients compared to those of patients diagnosed with stage-III-disease (P = 0.004), and its absence predicted significantly shorter overall survival (OS) in univariate analysis (P = 0.018). Absence of α6 integrin subunit protein expression using FCM predicted median OS of 12 months compared to 26 months for patients with tumors expressing the protein, although this finding did not reach significance (P = 0.27). In conclusion, as opposed to previous reports, both mRNA and protein expression of the α6 integrin subunit do not appear to be down-regulated in effusions compared to solid tumors. Loss of α6 integrin subunit mRNA (and possibly protein) expression is a novel prognostic marker in advanced-stage ovarian carcinoma. LBP mRNA and protein expression is independent of that of the α6 integrin subunit in both solid tumors and effusions of serous ovarian carcinoma. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of synthetic C-terminal fragment of interferon-2α on Daudi cells

Synthetic fragment of human interferon-2α (124th–138th amino acid residue, laboratory code 2438) inhibits the growth of B lymphocytes (Daudi cell line) in a dose-dependent manner. Radiolabeled peptide 2438 binds to specific receptors on the cell surface and competes with interferon-2α for the common binding sites. Translated fromByulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 123, No. 4, pp. 446–448, April, 1997     

Characterization of the human β4 nAChR gene and polymorphisms in CHRNA3 and CHRNB4

Most neuronal nicotinic acetylcholine receptors are heteropentamers, composed of α and β subunits. Mice lacking the α3 subunit and mice lacking both the β2 and β4 subunits, but not mice lacking the β2 or β4 subunits alone, have a severe phenotype characterized by megacystis, failure of bladder strips to contract in response to nicotine, widely dilated ocular pupils, growth failure, and perinatal mortality. The deficit in bladder contraction was also found in mice lacking only the β4 subunit, although they did not develop megacystis. The major bladder phenotype resembles the human autosomal recessive disorder of megacystis-microcolon-hypoperistalsis syndrome (MMIHS). Based on the similarity of the mouse and human phenotypes, we initiated mutation analyses in the α3 and β4 genes in MMIHS families. The human gene encoding the β4 subunit was fully characterized, including refinement of its mapping. Analysis of disease families and controls identified numerous genetic variants, including high-frequency polymorphisms in both CHRNA3 and CHRNB4. Although no loss-of-function mutations have been identified to date, these genes remain strong candidates for involvement in MMIHS, because various mutations might be obscured within the complex cluster of genes. Some of the markers presented here are valuable tools for analysis of the role of genetic variation in responses to nicotine and for characterization of various dysautonomic abnormalities. Received: February 19, 2001 / Accepted: March 16, 2001     

Interactions between the serotonergic and histaminergic systems in the central cardiovascular regulation in haemorrhage-shocked rats: involvement of 5-HT1A receptors

Aim and objective:  The aim of the work was to characterise the nAChRs on human PBMC. Method:  PBMC were isolated from human blood buffy coats provided by the blood transfusion service and were used for radioligand binding studies with [³H]-nicotine. RT-PCR experiments were used to determine nAChR subunit expression while immunoblotting experiments were used to confirm that nAChR subunits identified by RT-PCR were translated into protein. Results:  Binding studies suggested the presence of one binding site for (-)- nicotine on human peripheral blood lymphocytes. Competition studies showed that only (-)- nicotine, epibatidine and α-bungarotoxin, displaced radiolabelled nicotine from cells. RT-PCR studies demonstrated mRNA for α4, α5, α7, β1 and β2 nAChRs subunits in PBMC. Expression of mRNA for the a5 subunit of nAChR was observed in all lymphocyte samples tested. In contrast, the expression pattern of mRNAs for α4, α7, β1, and β2 mRNAs subunits of nAChRs, varied between samples. Western blot analysis showed that protein for α4, α5, and α7 and β2 nAChR subunits was expressed in most, but not all of the PBMC samples tested but some of the bands obtained were faint. Conclusion:  The results obtained suggest that human PBMC contain nAChRs containing α4β2, α4β2α5, and/or α7 subunits. Received 6 August 2008; returned for revision 3 September 2008; received from final revision 3 October 2008; accepted by M. Parnham 6 October 2008     

Alterations in NMDA receptor subunit densities and ligand binding to glycine recognition sites are associated with chronic anxiety in Alzheimer's disease

Glutamatergic deficits are established neuropathological features of Alzheimer's disease (AD) and are known to correlate with cognitive impairments. In contrast, the role of glutamatergic alterations in behavioral and psychological symptoms of dementia (BPSD) is unclear. There is considerable preclinical evidence for the importance of glycine recognition sites (GlyRS) of N-methyl-d-aspartate (NMDA) receptors in the regulation of anxiety behaviors. This study aimed to correlate several glutamatergic measures with chronic anxiety in AD. Twenty-one AD patients assessed by the Neuropsychiatric Inventory (NPI) were divided into low anxiety (LA) and high anxiety (HA) subgroups. GlyRS and NMDA channel were measured by brain homogenate binding with [³H]MDL105,519 and [³H]MK-801, respectively. Densities of NMDA receptor NR2A, NR2B and alternate spliced NR1 subunits were quantified by immunoblotting. We found that the binding affinity to GlyRS was significantly higher in HA compared to LA, and this higher GlyRS affinity correlated with selective reduction of NR2A density as well as with elevated anxiety scores. Our observations suggest a novel mechanism whereby subunit specific changes in the NMDA receptor complex may be linked to chronic anxiety in AD via effects on GlyRS function. We propose that NR2A and GlyRS should be further assessed as novel targets of behavioral pharmacotherapy in AD.     

Redox modulation of synaptic responses and plasticity in rat CA1 hippocampal neurons

Effects of redox reagents on excitatory and inhibitory synaptic responses as well as on the bidirectional plasticity of α-amino-3-hydroxy-5-methylisoxazole-propionic acid (AMPA) andN-methyl-d-aspartate (NMDA) receptor-mediated synaptic responses were studied in CA1 pyramidal neurons in rat hippocampal slices. The oxidizing agent 5,5′-dithiobis(2-nitrobenzoic acid) (DTNB, 200 μM) did not affect AMPA, GABA_A or GABA_B receptor-mediated synaptic responses or the activation of presynaptic metabotropic receptors. However, DTNB irreversibly decreased (by approximately 50%) currents evoked by focal application of NMDA. DTNB also decreased the NMDA component of the EPSC. The reversal potential of NMDA currents and the Mg²⁺ block were not modified. In the presence of physiological concentrations of Mg²⁺ (1.3 mM), DTNB did not affect the NMDA receptor-dependent induction of long-term potentiation (LTP) or long-term depression (LTD) expressed by AMPA receptors. In contrast, DTNB fully prevented LTP and LTD induced and expressed by NMDA receptors. Plasticity of NMDA receptor-mediated synaptic responses could be reinstated by the reducing agenttris-(2-carboxyethyl) phosphine (TCEP, 200 μM). These results suggest that persistent, bidirectional changes in synaptic currents mediated by NMDA receptors cannot be evoked when these receptors are in an oxidized state, whereas NMDA-dependent LTP and LTD are still expressed by AMPA receptors. Our observations raise the possibility of developing therapeutic agents that would prevent persistent excitotoxic enhancement of NMDA receptor-mediated events without blocking long-term modifications of AMPA receptor-mediated synaptic responses, thought to underlie memory processes.     

Age-related alterations in brain α1-adrenoceptors of hypertensive rats: Their possible role in the development of arterial hypertensionof hypertensive rats: Their possible role in the development of arterial hypertension

The binding of labeled agonist (³H-prazosin) to α₁-receptors in the frontal cortex, hypothalamus, and medulla oblongata of hypertensive (NISAG) and normotensive (Wistar) rats of different age is studied to elucidate the role of these receptors in the development of hereditary stress-induced arterial hypertension. It is found that the density of α₁-adrenoceptors in the hypothalamus of 30-day-old and adult NISAG rats is decreased, while in the medulla oblongata the number of these receptors, starting from the first week of life, is greater than in Wistar rats of the same age. From a comparison of these findings with the development of hypertension in NISAG rats it is concluded that α₁-adrenoceptors of the medulla oblongata are involved in this process. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 120, N ^o 7, pp. 78–80, July, 1995 Presented by V. P. Kaznacheev, Member of the Russian Academy of Medical Sciences