Receptor binding of glutamate in the striatum of rats differing in learning capacity.

A comparative investigation has been carried out for the first time of the receptor binding of glutamate with synaptic membranes and coarse fractions of the postsynaptic enlargements isolated from the striatum of rats differing in their capacity to develop an alimentary instrumental reflex. It was demonstrated that the number of that glutamate binding sites on the postsynaptic enlargements isolated from the striatum of rats capable of rapidly developing an alimentary instrumental reflex was increased as compared with animals not subjected to training. This relationship is maintained two months after the termination of training.

[The pharmacological characteristics, immunochemical identification and study of the location of quisqualate receptors in the rat and human brains]. / Farmakologicheskaia kharakteristika, immunokhimicheskaia identifikatsiia i issledovanie lokalizatsii kviskvalatnykh retseptorov golovnogo mozga krysy i cheloveka.

The kinetics of [3H]-L-glutamate binding to brain synaptic membranes (SM) and to glutamate-binding proteins (GBP) was determined with agonist and monoclonal antibodies (MAbs). It was revealed, that rat and human brain GBP have individual protein components with M(r) from 14 to 92 kDa. Quisqualate inhibited [3H]-L-glutamate binding to solubilized and to purified 68 kDa protein component. MAbs have the most activity, and NMDA was failure. It has been shown that 68 kDa component antigen determinants are similar to those of bovine, frog and rat brain synaptic membranes. Anti-GBP monoclonal antibodies blocked functional non-NMDA receptors in isolated frog spinal cord. Immunocytochemistry was done on rat and human brain sections. Distribution of quisqualate receptors was determined with light and electron microscopy. Some properties of vertebrate CNS non-NMDA receptors are discussed.

[Glutamate-binding membrane proteins from human platelets]. / Glutamatsviazyvaiushchie membrannye belki trombotsitov cheloveka.

Solubilization of the total membrane fraction of human platelets in a 2% solution of sodium deoxycholate and subsequent affinity chromatography on glutamate agarose resulted in two protein fractions possessing a glutamate-binding activity. As can be evidenced from radioligand binding data, the first fraction contains two types of binding sites (Kd1 = 1 microM, Bmax 1 = 100 pmol/mg of protein; Kd2 = 9.3 microMm Bmax2 = 395 pmol/mg of protein). The second fraction has only one type of binding sites (Kd = 1 microM, Bmax = = 110 pmol/mg of protein). SDS-PAAG electrophoresis revealed the presence in the first fraction of proteins with Mr of 14, 24, 56 and 155 kDa, whereas the second fraction was found to contain 14, 46, 71 and 155 kDa proteins. Solid phase immunoenzymatic analysis using poly- and monoclonal specific antibodies against mammalian brain glutamate-binding proteins revealed a marked immunochemical similarity of the isolated protein fractions with human brain synaptic membrane glutamate-binding proteins.

[The sites of high affinity binding of L-[3H]glutamic acid in human platelets. A new type of platelet receptor?]. / Uchastki vysokoaffinnogo sviazyvaniia L-[3H]glutaminovoi kisloty v trombotsitakh cheloveka. Novyi tip trombotsitarnogo retseptora?

The total membrane fraction of human platelets was found to contain high affinity sites of L-[3H]glutamic acid binding (Kd = 100 nM, Bmax = 1.06 pmol/mg protein). The pH optimum for binding is at pH approximately 6.9 Na+ (1-150 mM) inhibit glutamate binding by platelet membranes (IC50 = 12 mM). Ca2+ (50-100 microM) stimulate the binding by 10-20% and inhibit it by 20-30% at concentrations of 1-5 mM. Monoclonal antibodies to the glutamate receptor strongly suppress the L-[3H]glutamate binding by platelet membranes (IC50 = 300 nm). The presence in human platelets of a glutamate-sensitive receptor complex similar to the central nervous system glutamate receptor is postulated.

[Molecular organization of glutamate-sensitive chemoexcitatory membranes of nerve cells. Comparative analysis of glutamate-binding membrane proteins from the cerebral cortex of rats and humans]. / Molekuliarnaia organizatsiia glutamatchuvstvitel'nykh khemovozbudimykh membran nervnykh kletok. Sravnitel'nyi analiz glutamatsviazyvaiushchikh membrannykh belkov kory golovnogo mozga krys i cheloveka.

The kinetics of 3H-L-glutamate binding to human brain synaptic membranes revealed the existence of one type of binding sites with Kd and Vmax comparable with those for freshly isolated rat brain membranes. The fraction of glutamate-binding proteins (GBP) was shown to contain three components with Mr of 14, 60 and 280 kD whose stoichiometry is specific for human and rat brain. All fractions were found to bind the radiolabeled neurotransmitter and to dissociate into subunits with Mr of 14 kD after treatment with-potent detergents (with the exception of the 56-60 kD component). Study of association-dissociation of GBP protein subunits by high performance liquid chromatography confirmed the hypothesis on the oligomeric structure of glutamate receptors which are made up of low molecular weight glycoprotein-lipid subunits and which form ionic channels by way of repeated association. Despite the similarity of antigen determinants in the active center of glutamate receptors from human and rat brain, it was assumed that the stoichiometry of structural organization of receptor subunits isolated from different sources is different. The functional role of structural complexity of human brain glutamate receptors is discussed.

[Isolation and partial purification of the endogenous inhibitor of receptor binding of 3H-L-glutamate]. / Vydelenie i chastichnaia ochistka éndogennogo ingibitora retseptornogo sviazyvaniia 3H-L-glutamata.

The endogenous factor that inhibited 3H-L-glutamate specific binding (FIB) was isolated from the aqueous extract of the crude mitochondrial fraction of the rat cerebral cortex homogenate and partially purified. The purification procedure involved several steps of ion-exchange, gel-permeating and thin-layer chromatography. Partially purified FIB competitively inhibited 3H-L-glutamate specific binding and had the molecular weight of 450-600 Da. Glutamic acid residues were found in FIB amino acids. The functional role of the isolated factor as an endogenous modulator involved in the regulation of effective synaptic transmission of glutamatergic brain synapses is discussed.

[The function of glutamate receptors in the membrane vesicules, proteoliposomes and hybrid cells of the neuroblastoma N18Tg2a]. / Funktsii glutamatnykh retseptorov v membrannykh vezikulakh, proteoliposomakh i gibridnykh kletkakh neiroblastomy N18Tg2a.

The transport and selective functions of the glutamate-binding proteins of the rat brain cortex synaptic membranes, were studied. The data on kinetics of absorption of the ions 22Na+, 86Rb+ and 45Ca++ by the membrane vesicles and liposomes containing receptor proteins, are presented. The specific features of the c. n. s. glutamate receptors functioning in the hybrid cells of the neuroblastoma N18Tg2a, are revealed. A selective activation of transport of the 22Na+ ions was found in this kind of model systems in presence of physiological concentrations of L-glutamate. The modelling of the glutamate receptors function depended on composition of lipids, presence of the endogenous peptide agent inhibiting binding of the H3-L-glutamate, and on the degree of the neuroblastoma differentiation. Monoclonal antibodies obtained for the receptor's recognizing areas blocked the functions of the glutamate-binding proteins in all the model systems.

[Molecular organization of glutamate-sensitive chemoexcitatory membranes of nerve cells. Binding of L-[3H]glutamate to synaptic membranes of the rat cerebral cortex]. / Molekuliarnaia organizatsiia glutamatchuvstvitel'nykh khemovozbudimykhmembran nervnykh kletok. Sviazyvanie L-[3H]glutamata s sinapticheskim membranami kory golovnogo mozga krys.

The binding of L-[3H]glutamate to rat cerebral cortex synaptic membranes was investigated. Two types of binding sites, a Na+-independent (Kd = 140-160 nm; Bmax = 3.8-4.5 pmol-mg of protein) and a Na+-dependent (Kd = 2.0 microM; Bmax = 45-50 pmol/mg of protein) ones, were detected. The dependence of Na+-insensitive binding on time and temperature and membrane content in a sample was determined. Mono- and divalent cations (5-10 mM) potentiated specific binding by 2.1-3.3 times. The Na+-dependent binding is associated with active transport systems, while the Na+-independent one-with true receptor binding. The relationship between CNS glutamate receptors and Na+-independent binding sites is discussed.

[3H-1-glutamate binding with the synaptic membranes isolated from the cerebral cortex and hippocampus of Krushinskii-Molodkina strain rats]. / Sviazyvanie 3H-1-glutamata s sinapticheskimi membranami, vydelennymi iz kory bol'shikh polusharii i gippokampa krys linii Krushinskogo-Molodkinoi.

Specific binding of 3H-L-glutamate to synaptic membranes isolated from the cerebral cortex and hippocamp of Wistar and Krushinsky-Molodkina (KM) rats examined both in a quiet awake state and after audiogenic seizures was compared. The dissociation constant (KD) values and binding capacity (Bmax) for KM rats did not differ significantly from the corresponding parameters of binding determined for Wistar rats (KD--89.8 +/- 18.1 and 102.6 +/- 12.5 nm, Bmax--1.23 +/- +/- 0.08 and 1.30 +/- 0.15 pmol/mg for the cortex and hippocamp, respectively). After audiogenic seizures the binding capacity of the hippocamp of KM rats was reduced by 30%. It is suggested that hippocampal glutamate receptors of KM rats are involved in the mechanism of convulsive activity formation.