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M Hirouchi

Publications and source records attributed to M Hirouchi.

At least 19 recordsLinked to original sources
PubMed2001

Reversal by NS-7, a neuroprotective compound, of the decrease in transcription factor CREB mRNA expression in rat brain after permanent middle cerebral artery occlusion.

The effect of a neuroprotective agent NS-7 on changes in mRNA expressions for cyclic AMP responsive element binding protein (CREB) and several neurotrophins was examined in the rat cerebral cortex after permanent middle cerebral artery occlusion (MCAO). Significant reduction in mRNA expressions for CREB was observed at 24h after MCAO. NS-7 (0.5mg/kg), when injected at 6h after MCAO, significantly reversed the decreased expression for CREB mRNA. In addition, the mRNA expression for basic fibroblast growth factor (bFGF) was also significantly enhanced by NS-7 in MCA-occluded but not in sham-operated rats. On the other hand, the mRNAs for interluekin-6 and inducible-type nitric oxide synthase were markedly induced in the cerebral cortex of MCA-occluded rats, which was not significantly reversed by NS-7. Therefore, it is suggested that the reversal of decrease in CREB mRNA and concomitant increase in mRNA expression for bFGF may contribute to the neuroprotective action of NS-7.

Animals↗
PubMed2000

Involvement of peroxynitrite and hydroxyradical generated from nitric oxide in hypoxia/reoxygenation injury in rat cerebrocortical slices.

The changes in nitric oxide (NO) formation during hypoxia and reoxygenation were measured in slices of rat cerebral cortex, and the possible involvement of NO and its decomposition products, including peroxynitrite and hydroxyradical, in the hypoxia/reoxygenation injury was subsequently investigated. NO formation estimated from cGMP accumulation in the extracellular fluids was enhanced during hypoxia and to a lesser extent in the reoxygenation period. The mRNA for inducible NO synthase (NOS) was detected 3-5 h after reoxygenation, although neuronal NOS mRNA decreased after reoxygenation. Several NOS inhibitors such as N(G)-monomethyl-L-arginine and N(G)-nitro-L-arginine blocked not only the NO formation but also the hypoxia/reoxygenation injury as determined by lactate dehydrogenase (LDH) leakage. The hypoxia/reoxygenation injury was prevented by peroxynitrite scavengers including deferoxamine and uric acid, or several hydroxyradical scavengers such as dimethylthiourea, 2-mercaptopropionylglycine and D(-) mannitol. In addition, the hypoxia/reoxygenation injury was attenuated by poly(ADP-ribose)synthetase inhibitors such as banzamide, 3-aminobenzamide and 1,5-isoquinolinediol. On the other hand, both N-morpholinosidnonimine, a peroxynitrite generator, and hydroxyradical-liberating solution containing FeCl(3)-ADP and dihydroxyfumarate caused a marked LDH leakage in normoxic slices. These findings suggest that the enhanced formation of NO causes hypoxia/reoxygenation injury after degradation to peroxynitrite and hydroxyradical and the resultant activation of poly(ADP-ribose)synthetase.

Adenosine Triphosphate↗
PubMed2000

Role of metabotropic glutamate receptor subclasses in modulation of adenylyl cyclase activity by a nootropic NS-105.

The involvement of metabotropic glutamate (mGlu) receptors in the modulatory actions of a novel cognition enhancer, (+)-5-oxo-D-prolinepiperidinamide monohydrate (NS-105), on adenylyl cyclase activity in rat cerebrocortical membranes and primary neuronal cultures was investigated using selective antagonists and antisense oligodeoxynucleotides for mGlu receptor subclasses. In rat cerebrocortical membranes, the inhibitory action of NS-105 (0.1 microM) on forskolin-stimulated cAMP formation was blocked by a group II mGlu receptor antagonist, (+/-)-alpha-ethylglutamic acid, and by a group III antagonist, (+)-2-amino-2-methyl-4-phosphonobutanoic acid (MAP-4), but not by a group I antagonist, (+/-)-1-aminoindan-1,5-dicarboxylic acid (AIDA), whereas the facilitation of cAMP formation by NS-105 (1 microM) in pertussis toxin-pretreated membranes was abolished by AIDA but not by (+/-)-alpha-ethylglutamic acid or MAP-4. In primary cultured neurons of mouse cerebral cortex, the inhibitory action of NS-105 on adenylyl cyclase activity disappeared after treatment with antisense oligodeoxynucleotides for group II (mGlu(2) and mGlu(3) receptors) and group III (mGlu(4) and mGlu(7) receptors) but not group I (mGlu(5) receptor) mGlu receptor subclasses. These findings suggest that the inhibitory action of NS-105 on adenylyl cyclase activity is mediated through group II and group III mGlu receptor subclasses while the facilitatory action is dependent on the group I mGlu receptor subclass.

Adenylyl Cyclases↗
PubMed2000

Neurochemical and molecular pharmacological aspects of the GABA(B) receptor.

Metabotropic gamma-aminobutyric acid (GABA)B receptors are known to modulate the synaptic release of various neurotransmitters in the nervous system. Activation of GABA(B) receptor induces the inhibition of adenylyl cyclase activity, while it does not stimulate the formation of inositol phosphates. Activation of a potassium conductance and suppression of a calcium conductance are also recognized, similarly to some of G protein-coupled receptors. Recent molecular cloning has revealed that GABA(B) receptor possesses a large extracellular domain including the binding site for GABA and seven transmembrane domains. Their molecular structures in the brain are unique and interesting because of heterodimerization consisting of two distinct genes: GABABR1 and GABABR2. Such assembled receptors can be classified as a novel type of the metabotropic receptor superfamily.

Adenylyl Cyclases↗
PubMed1997

Functional coupling of Gi subtype with GABAB receptor/adenylyl cyclase system: analysis using a reconstituted system with purified GTP-binding protein from bovine cerebral cortex.

A single molecular species of GTP-binding protein (G protein) has been purified from the bovine cerebral cortex. The immunoblot analysis indicated that the isolated G protein might be Gi1 or Gi2 but not Go, since it was reacted by specific antibodies, anti-Gi alpha 1-2 and anti-Gi alpha 1-1, but not anti-Go alpha. When the Gi protein was reconstituted into phospholipid vesicles with partially purified GABAB receptor and adenylyl cyclase, the stimulation of GABAB receptor by its agonists induced the inhibition of forskolin-stimulated cAMP accumulation. This GABA-induced inhibition was abolished by CGP 55845A, an antagonist of GABAB receptor. These results suggest that a Gi subtype, which was suggested to correspond to Gi1 or Gi2 may be functionally coupled with GABAB receptor/adenylyl cyclase system.

Adenylyl Cyclases↗
PubMed1995

[Recent advances in studies of GABA receptors: neurochemical aspects].

gamma-Aminobutyric acid (GABA) has been established as a major inhibitory neurotransmitter in the brain. The GABA-induced inhibitory transmission is mediated by two distinct types of GABA receptors which are termed as GABAA and GABAA receptors. The GABAA receptor forms a Cl- channel that consists of several subunits. The recent development of molecular cloning clarified the presence of multiple and heterogeneous molecules in the GABAA receptor subunits. Therefore, it is suggested that multiple GABAB receptors generate various functions in the brain. In contrast, the GABAB receptor exhibits various metabotropic actions for the inhibitory neurotransmission, since it is coupled with GTP-binding proteins. The GABAB receptor of approximately 80 kDa protein in its molecular weight was purified from the bovine cerebral cortex and the presence of another molecular species of the GABAB receptor was also suspected. These results indicate that studies on the molecular diversity of the GABA receptors is important for elucidating the functional roles of GABAergic neurons in the brain.

Amino Acid Sequence↗
PubMed1994

Association and agonistic action of DN-2327, a novel isoindoline derivative, GABAB receptor in brain.

The association and action of DN-2327, 2-(7-chloro-1,8-naphthyridin-2-yl)-3-[(1,4-dioxa-8- azaspiro[4,5]dec-8-yl)carbonylmethyl]isoindolin-1-one, on the gamma-aminobutyric acid (GABA)B receptor in rat brain have been examined. DN-2327 inhibited the binding of [3H]GABA to GABAB receptor in crude synaptic membrane obtained from rat brain. The Scatchard analysis of [3H]GABA binding to GABAB receptor indicated that DN-2327 induced the decrease in affinity of both high and low affinity binding sites without changing the Bmax values. The forskolin-stimulated adenylate cyclase activity in slices from rat cerebral cortex was significantly suppressed by the addition of DN-2327. Furthermore, this inhibition by DN-2327 was eliminated by the simultaneous additions of 2-hydroxy saclofen or CGP 55845A, GABAB receptor antagonists. These results suggest that DN-2327 may have not only a high association with GABAB receptor but also an agonistic action on the receptor.

Adenylyl Cyclases↗
PubMed1994

Effects of thyroxine and its related compounds on cerebral GABA receptors: inhibitory action on benzodiazepine recognition site in GABAA receptor complex.

The effects of thyroxine and its related derivatives on gamma-aminobutyric acid (GABA) receptors in the rat brain were examined. D-Thyroxine strongly inhibited [3H]flunitrazepam binding to benzodiazepine receptor in crude synaptic membrane from the rat brain. The Scatchard analysis of the [3H]flunitrazepam binding in the presence of D-thyroxine indicated the decreases in the affinity and maximum number of binding site. Furthermore, D-thyroxine inhibited the enhancing effect of flunitrazepam on GABA-stimulated 36Cl- influx into membrane vesicles, although GABA-stimulated 36Cl- influx alone was not affected by D-thyroxine. On the other hand, the effects of thyroxine and its related derivatives on cerebral GABAB receptor binding were not noted. These results suggest that D-thyroxine may be a drug which is able to modulate the function of GABAA receptor complex via the inhibitory action on benzodiazepine recognition site.

Animals↗
PubMed1994

[Molecular pharmacology of GABAA and GABAB receptors].

The receptor for gamma-aminobutyric acid (GABA), a major inhibitory neurotransmitter in the mammalian brain, has been classified into GABAA and GABAB subtypes. The GABAA receptor forms a Cl- channel and is consisted of several subunits. These subunits in the brain are known to be multiple and heterogeneous in their molecular structure. Therefore, it is suggested that these multiple GABAA receptors generate various inhibitory functions in the brain. In contrast, the GABAB receptor is known to be one of the metabotropic type of receptors which generate slow inhibitory postsynaptic potentials and functionally couple with Gi/Go types of GTP-binding proteins. The GABAB receptor in the brain has been purified to homogeneity using immunoaffinity purification procedures and found to be an 80-kDa protein. The possible existence of multiplicity in the cerebral GABAB receptor has also been suggested.

Animals↗
PubMed1994

Alteration in cerebral GABAB receptor functions during formation of alcohol dependence.

Alterations in the function of cerebral GABAB receptor systems were studied in alcohol dependent animals and reconstituted GABAB receptor systems in vitro. The GABAB receptor binding at both high and low affinity sites showed a significant increase during the formation of alcohol dependence and alcohol withdrawal, although ethanol at a low concentration did not affect the GABAB receptor binding in vitro. On the other hand, a low concentration (100 mM) of ethanol, which had no significant effect on GABAB receptor binding, inhibited cAMP accumulation in vitro. The cAMP formation in brain did not show significant changes during the formation of alcohol dependence in spite of the increase in GABAB receptor binding. These results indicate that alcohol dependence induces an increase of GABAB receptor binding in the brain. This increase in GABAB receptor binding, however, may not be associated with the changes in the GABAB receptor mediated suppression of cAMP formation, possibly due to the deterioration of the coupling between the GABAB receptor and the Gi/Go type of GTP binding protein/adenylyl cyclase. Furthermore, the present results suggest that in vitro addition of ethanol may have differential effects on cerebral GABAB receptor systems as compared with those found in the brain of alcohol dependent subjects.

Administration, Inhalation↗
PubMed1993

Alteration of GABAA receptor alpha 1-subunit mRNA in mouse brain following continuous ethanol inhalation.

Alterations in the expression of mRNA for GABAA receptor alpha 1-subunit were analyzed in the brain using mice that had been made alcohol-dependent, and exhibited a decrease in GABA-dependent 36Cl- influx into membrane vesicles following continuous ethanol inhalation for 7 days. Continuous ethanol inhalation for more than 5 days induced a significant increase in the expression of GABAA receptor alpha 1-subunit mRNA in the brain without significantly altering total poly(A)+ RNA content. Furthermore, it was found that the increase in expression of GABAA receptor alpha 1-subunit mRNA in the brain turned to its normal level 8 h after the ethanol inhalation was terminated. In contrast, the expression of beta-actin mRNA in the brain was not altered under the same experimental conditions. These results suggest that continuous ethanol inhalation may induce not only the suppression of the functions of GABAA receptor complex but also a reactive increase in the expression of mRNA for GABAA receptor subunits in the brain.

Actins↗
PubMed1993

Structure and function of cerebral GABAA and GABAB receptors.

The receptor for GABA (gamma-aminobutyric acid), an inhibitory neurotransmitter in the brain, has been classified into GABAA and GABAB types. The GABAA receptor was purified by means of affinity column chromatography using benzodiazepine as an immobilized ligand. The results indicated that the GABAA receptor consists of several subunits and forms a GABA-gated Cl- channel, which is coupled with the benzodiazepine receptor. The molecular weight of the GABAA receptor complex was estimated to be approximately 300 kDa. Furthermore, cDNA cloning of GABAA receptor subunits was performed and the primary structure of these subunits was deduced. The results suggested that these subunits possess four transmembrane domains in their structure which are important for the formation of the Cl- channel. On the other hand, activation of GABAB receptors induced the inhibition of adenylyl cyclase activity and phosphatidylinositol turnover via inhibitory GTP-binding proteins such as G(i) and/or G(o). The GABAB receptor was purified using baclofen affinity and immunoaffinity column chromatographies. It was confirmed that the purified GABAB receptor protein is about 80 kDa in its molecular weight. This protein is capable of inducing the inhibition of adenylyl cyclase when it is reconstituted with G(i)/G(o) protein in the phospholipid vesicle system. Currently available data indicate that GABAA and GABAB receptors in the central nervous system are distinct not only in terms of their molecules but also their signal transduction systems. However, the primary structure and synaptic localization of GABAB receptor molecules in the brain remain to be clarified.

Amino Acid Sequence↗
PubMed1993

Functional alterations in GABAA receptor complex induced by ethanol.

Possible direct actions of ethanol on cerebral GABAA receptor complex have been analyzed using purified GABAA receptor complex from the bovine cerebral cortex and its reconstituted vesicles. Addition of ethanol to the reconstituted vesicles with purified GABAA receptor complex induced a significant increase of GABA-dependent 36Cl- influx. Furthermore, the reconstituted GABAA receptor pretreated with 20 mM ethanol, which had no effect on GABAA receptor binding, also showed an increase of the GABA-dependent 36Cl- influx. On the other hand, the GABA-dependent 36Cl- influx into membrane vesicles prepared from alcohol dependent mouse brain showed a significant decrease, although this decrease was found to be recovered at 8 hours after the withdrawal of ethanol inhalation. Moreover, the expression of mRNA for GABAA receptor alpha 1-subunit in the brain showed an elevation in alcohol dependent condition, although this elevation was recovered to the control level after the withdrawal of alcohol inhalation. The present results suggest that continuous inhalation of ethanol in vivo may induce not only the alterations in the function of GABAA receptor complex but also that in the expression of mRNA for the receptor in the brain.

Alcoholism↗
PubMed1992

Muscimol-induced reduction of GABAA receptor alpha 1-subunit mRNA in primary cultured cerebral cortical neurons.

The expression of mRNA for GABAA receptor alpha 1-subunit in mouse cerebral cortical neurons in primary culture was examined using RNA blot analysis and ribonuclease protection assay following the treatment of neurons with muscimol, a selective agonist of GABAA receptor. The level of mRNA for GABAA receptor alpha 1-subunit showed a decrease in comparison with that in non-treated cells, whereas no changes in the level of beta-actin mRNA were noted under the same experimental conditions. This muscimol-induced reduction in GABAA receptor alpha 1-subunit mRNA was counteracted by the simultaneous exposure of neurons to both bicuculline, an antagonist of GABAA receptor, and muscimol. The expression of mRNA for GABAA receptor alpha 1-subunit also showed a decline by the treatment of cells with flunitrazepam alone, an agonist of benzodiazepine receptor, and this change was also abolished by the simultaneous exposure of cells to flunitrazepam and Ro15-1788, an antagonist for central benzodiazepine receptor. These results suggest that the continuous stimulation of cerebral GABAA receptor complex may induce the reduced expression of mRNA for the receptor complex.

Animals↗
PubMed1992

Characteristics of the association of brotizolam, a thieno-triazolo diazepine derivative, with the benzodiazepine receptor: a selective and high affinity ligand of the central type I benzodiazepine receptor.

Characteristics of the association of brotizolam, a thieno-triazolo diazepine derivative, to central benzodiazepine receptors were examined. Brotizolam significantly displaced the [3H]flunitrazepam and [3H]beta-carboline carboxylate ethylester bindings to crude synaptic membrane from the rat brain. This agent had the highest affinity for benzodiazepine receptors in the cerebellum, and it was found to be 2.1 times that in the spinal cord. Furthermore, a low concentration of brotizolam potentiated the GABA-stimulated 36Cl- influx into membrane vesicles. In contrast, the bindings of [3H]8-hydroxy-2-(di-n-propylamino)tetralin to 5-hydroxytryptamine1A receptors and [3H]ketanserin to 5-hydroxytryptamine2 receptors were not affected by brotizolam. The present results suggest that brotizolam may be a selective and high affinity ligand for the type I central benzodiazepine receptor. The anxiolytic and hypnotic actions of brotizolam seem to be not due to the association with 5-hydroxytryptamine receptor, but due to the activation of the GABAA receptor complex. Furthermore, the present results suggest that the lower affinity of brotizolam to benzodiazepine receptors in the spinal cord than those in the cerebellum may be related to the low muscle relaxation action of this drug.

Animals↗
PubMed1991

Expression of mRNA for Gs alpha and Gi2 alpha in primary cultured mouse cerebral cortical neurons.

Developmental changes of mRNAs for alpha-subunits of GTP binding protein (G-protein) such as Gs alpha and Gi2 alpha during neuronal development were examined in both primary cultured cerebral cortical neurons and cerebral cortices obtained from age-matched mice. The expression of mRNAs for both G-protein alpha-subunits in primary cultured neurons showed a development pattern similar to that in the cerebral cortex in vivo. Both mRNAs were expressed at an early stage of neuronal development, and the expression patterns of mRNA for both G-protein alpha-subunits were found to be only slightly changed during development. These results suggest that the G-protein appears at an early stage of neuronal development and may play an important role therein.

Animals↗
PubMed1991

[Expression and regulation of GABA receptors in the brain].

GABA receptors are classified into two receptor subtypes: GABAA and GABAB receptors. The GABAA receptor, one of the ionotropic type receptors, is formed by various subunits (alpha, beta, gamma and delta subunits) and constitutes the GABA-gated Cl- channel. The different combinations of these subunits are known to produce functionally heterogeneous GABAA receptors both pharmacologically and physiologically. On the other hand, GABAB receptor is known to be metabotropic type which is negatively coupled with adenylate cyclase and inositol phosphate turnover systems via inhibitory GTP binding protein.

Animals↗