Biomedical subjects

N Akaike

Publications and source records attributed to N Akaike.

At least 145 records · Page 8Linked to original sources

PubMed1995

MAO inhibitors, clorgyline and lazabemide, prevent hydroxyl radical generation caused by brain ischemia/reperfusion in mice.

The effects of clorgyline, the MAO-A inhibitor, and lazabemide, the MAO-B inhibitor, on the levels of the hydroxyl radicals appearing in the cerebral ventricles of mice during brain ischemia/reperfusion were examined by using a salicylate trapping method. The amount of hydroxyl radicals formed peaked at 20 min after reperfusion (approximately 150% vs. basal level). The dopamine level markedly increased shortly after the initiation of an ischemic insult and thereafter waned. By contrast, the concentration of 3,4-dihydroxyphenylacetic acid (DOPAC) level decreased during a 40-min period of ischemia, gradually returning to the preischemic basal level upon reperfusion. The ischemia reperfusion-induced hydroxyl radical generation was attenuated by 3 mg/kg of clorgyline and lazabemide. Furthermore, mice pretreated with these MAO inhibitors showed decreased DOPAC levels in comparison with those of their respective vehicle-treated control groups; recovery of the reduced DOPAC level was also delayed. In conclusion, it is likely that both type A and type B MAOs participate in the generation of hydroxyl radicals during brain ischemia/reperfusion. This finding suggests the possible use of MAO inhibitors as neuroprotective agents for treating ischemic injury.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1994

Effects of plant diterpenes on the neuronal GABAA receptor-operated chloride current.

The effects of plant diterpenes, horminone (HMN) and taxodione (TXN), on the GABAA receptor-operated Cl-current (IGABA) were investigated in voltage-clamped and internally perfused neurones dissociated from frog dorsal root ganglia. Both diterpenes depressed IGABA in a concentration-dependent manner similar to that of picrotoxin. Concentrations required to elicit 50% depression of the IGABA were 10(-6) M for picrotoxin, 10(-5) M for HMN and 10(-4) M for TXN. Blocking and restoration kinetics of the IGABA with HMN were also similar to those of picrotoxin. Time constants for both the blockade and restoration of the IGABA with TXN were more than five times greater than those with HMN.

Abietanes↗

PubMed1994

Flow cytometric analysis on cytotoxic action of amyloid beta protein fragment 25-35 on brain neurons dissociated from the rats.

Effects of amyloid beta protein fragment 25-35, A beta P(25-35), on membrane permeability and cell viability were examined in the brain neurons dissociated from the rats using a flow cytometer and two fluorescent dyes, fluo-3 to monitor intracellular Ca2+ concentration ([Ca2+]i) of neurons and ethidium which is impermeant to membranes of intact neurons to stain dead and dying neurons. A beta P(25-35) augmented fluo-3 fluorescence of some neurons at concentrations greater than 1 microM, indicating an increase in [Ca2+]i although other neurons (about 80% of total neurons) did not respond to A beta P(25-35) even at 10 microM. A beta P(25-35) at 1 microM or greater increased dose-dependently the number of ethidium-stained neurons, suggesting a dose-dependent increase in number of dead and dying neurons. Results suggest that A beta P(25-35) increases the membrane permeability of brain neurons, resulting in a destabilized intracellular homeostasis that leads to neuonal death.

Amyloid beta-Peptides↗

PubMed1994

Amyloid beta protein-induced irreversible current in rat cortical neurones.

The effect of amyloid beta protein (A beta P) was examined in neurones dissociated from rat cortex using the nystatin perforated patch-clamp technique. A beta P at concentrations > 10 nM induced an irreversible slow inward current associated with an increase in membrane conductance. The time lag until the appearance of the effect of A beta P shortened in a concentration-dependent manner. When extracellular Na+ and Cl-, and intracellular K+ were replaced by equimolar N-methyl glucamine, isothionate- and Cs+, respectively, the membrane conductance and the reversal potential were not affected. Even when an internal solution including 1,2-bis(O-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (20 mM) was used, the effect of A beta P did not alter. It is suggested that A beta P binds to the neuronal membrane and opens non-selective ion channels, resulting in neuronal degeneration.

Amyloid beta-Peptides↗

PubMed1994

Ionic properties of IK,n in outer hair cells of guinea pig cochlea.

The ionic properties of voltage-dependent K+ current activated at the resting membrane potential (IK,n) of outer hair cells (OHC) isolated from the guinea pig cochlea were studied using a patch-clamp technique in a whole-cell recording mode. The reversal potential of IK,n indicated a high selectivity for K+, and the relative permeability ratios for various monovalent cations were K+:Rb+:NH4+ = 1:1.21:0.13. Decrease in extracellular Cl- inhibited the IK,n. IK,n was blocked by Cs+ and Ba2+, although the inhibitory manner of Cs+ and Ba2+ were voltage-dependent and voltage-independent, respectively. By the use of puff-application method, the local application of Ba2+ to basolateral surface of OHC shifted the holding current level in an inward direction, whereas the application to apex and hair showed little change. Indicating that the IK,n channels preferentially locate at the basolateral region of cell membrane.

Ammonia↗

PubMed1994

Regulation of K+ conductance by histamine H1 and H2 receptors in neurones dissociated from rat neostriatum.

1. The effects of histamine on dissociated neostriatal neurones of the rat were investigated in the whole-cell mode using the nystatin-perforated patch recording technique. 2. Histamine evoked a net inward current accompanied by a decrease in the membrane conductance at a holding potential (Vh) of -44 mV. This response was observed in neurones considered to be interneurones based on morphology, membrane properties and the responsiveness to acetylcholine. 3. A net inward current evoked by 10(-8) to 10(-6) M histamine was inhibited in a concentration-dependent manner by the H1 receptor antagonists, pyrilamine and triprolidine. The H1 receptor agonists, 2-methylhistamine and 2-thiazolylethylamine, mimicked the histamine response, indicating that this response was mediated by the H1 receptor. 4. Histamine, at high concentrations between 10(-6) and 10(-5) M, evoked an additional net inward current with a decrease in the membrane conductance, which was inhibited by the H2 receptor antagonists, cimetidine, ranitidine and famotidine. The H2 receptor agonist, impromidine, partially mimicked the response. Thus, this additional current was considered to be mediated by the H2 receptor. 5. The reversal potentials for H1 and H2 receptor-operated currents shifted 56.9 and 59.3 mV for a 10-fold change in [K+]o, respectively, suggesting that these currents were carried by K+. 6. An analysis of change in current fluctuations mediated by H1 and H2 receptors suggested that the unitary current amplitudes of K+ channels linked to H1 and H2 receptors were 0.29 +/- 0.06 (n = 4) and 0.27 +/- 0.07 pA (n = 4), respectively. There was no significant difference between these values. The estimated mean life times (tau) for both channels were also identical (1.1 ms). 7. It was concluded that histamine reduces K+ currents in neostriatal interneurones and that both H1 and H2 receptors are involved in the response.

Animals↗

PubMed1994

Nicotinic and muscarinic acetylcholine responses in the embryo chick ciliary ganglion cells.

Nicotinic and muscarinic acetylcholine (ACh) responses were investigated in acutely dissociated chick ciliary ganglion neurons using the nystatin perforated patch clamp technique. ACh-induced a rapid transient inward current in 100% of the neurons at a holding potential of -60 mV. This rapid inward current was mimicked by nicotine but not by muscarine. The reversal potential of the rapid inward current was +10.5 mV and the current was inhibited by d-tubocurarine and hexamethonium in a dose-dependent manner. In 57.6% of neurons, a slow inward current was also induced by ACh at a holding potential of -20 mV. This slow inward current was mimicked by muscarine but not by nicotine. The slow inward current became smaller at a hyperpolarized potential but not reversed, being consistent with the fact that this current was elicited by the inhibition of M-current. p-Fluorohexa-hydrosiladifenidol (P-F-HHSiD) strongly inhibited the slow inward current, suggesting that the current was elicited by the activation of M3 receptors.

Acetylcholine↗

PubMed1994

FCCP modulation of Ca2+ oscillation in rat megakaryocytes.

The effects of a mitochondrial uncoupler, FCCP, (carbonyl cyanide-p-trifluromethoxyphenyl-hydrazone) on the regulation of cytoplasmic Ca2+ were investigated in ATP-induced Ca2+ oscillation system of rat megakaryocyte. Application of FCCP did not induce any detectable Ca(2+)-activated K+ current (IKCa) but pretreatment with FCCP modulated the ATP-induced repetitive IKCa. FCCP abolished the IKCa induced by low concentrations of ATP. However, when the concentration of ATP was high, the uncoupler also changed the periodic current to a sustained one. Similar biphasic regulation by the uncoupler was observed in the case of IP3-evoked repetitive IKCa. These results indicate that FCCP inhibits both Ca2+ mobilization and elimination processes after IP3 liberation induced by agonist stimulation.

Adenosine Triphosphate↗

PubMed1994

Amino acid-induced responses in CNS neurons of normal mouse and Wriggle Mouse Sagami.

Amino acid-induced responses and their regional heterogeneities in the motor cortical and hippocampal (CA1) neurons of normal mouse and Wriggle Mouse Sagami (WMS) were studied by conventional patch-clamp techniques. There were no differences in the current densities and EC50s of glutamate-, gamma-amino butyric acid (GABA)-, and glycine-induced responses between the two groups of mice. In both types of mice, the GABA-induced current density of cortical neurones was higher and EC50 was lower than in hippocampal neurones, whereas the responses induced by glycine and glutamate did not show any differences.

Animals↗

PubMed1994

Cisplatin blocks voltage-dependent calcium current in dissociated outer hair cells of guinea-pig cochlea.

The effect of the ototoxic molecule cisplatin (cis-DDP) on the voltage-dependent Ca2+ channel in dissociated outer hair cells (OHCs) of guinea-pig cochlea was investigated using a whole-cell patch-clamp technique. Cis-DDP had antagonistic effect on the Ca2+ channel and reversibly suppressed the Ca2+ current in a concentration-dependent manner. These results suggested that one of the ototoxic mechanisms of cis-DDP is involved in the inhibition of the Ca2+ channel in OHCs.

Animals↗

PubMed1994

Developmental change in voltage dependency of NMDA receptor-mediated response in nucleus tractus solitarii neurons.

The developmental change of Mg2+ block of NMDA-induced response (INMDA) was investigated in the freshly dissociated nucleus tractus solitarii (NTS) neurons of the rats by the use of a nystatin-perforated patch-recording configuration. Mg2+ block was less obvious in a number of fetal NTS neurons than in the neurons of > 9 days after birth (P9) and became rapidly apparent by P3. Protein kinase C (PKC) modulators, such as staurosporine, H-7 and phorbol ester, did not clearly affect the generation of the voltage dependency of INMDA in immature rats. In addition, the facilitatory effect of glycine on the INMDA did not change in development. These evidences suggest that an appearance of the voltage dependency of INMDA in NTS neurons might be due to a developmental change in combinations of subunits composing the NMDA receptor and/or in the intracellular modulators of the INMDA other than PKC.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1994

Sevoflurane-induced ionic current in acutely dissociated CA1 pyramidal neurons of the rat hippocampus.

The electrophysiological properties of sevoflurane (Sev)-induced current (ISev) were investigated in CA1 pyramidal neurons freshly dissociated from the rat hippocampus by using the nystatin perforated patch recording configuration under voltage-clamp condition. Within the range of Sev concentrations from 3 x 10(-4) to 2 x 10(-3) M, ISev was an inward current which consisted of an initial transient peak component and a successive steady-state plateau component. The peak current component increased in a concentration-dependent manner with a conductance increase. The application of Sev over 2 x 10(-3) M, however, suppressed the peak and steady-state current components with a concomitant decrease in conductance and elicited a transient inward current ('hump' current) immediately after wash out. The current-voltage relationship for ISev showed some outward rectification suggesting a slight voltage-dependency of the ISev. The reversal potential of ISev (ESev) was close to the ECl and shifted by 52 mV for a 10-fold change in extracellular Cl- concentrations, indicating that ISev is passing through Cl- channels. The single channel conductance obtained from the analysis of the variance of ISev fluctuations was 15.3 +/- 1.3 pS.

Animals↗

PubMed1994

Effects of lindane (gamma-BHC) and related convulsants on GABAA receptor-operated chloride channels in frog dorsal root ganglion neurons.

Effects of lindane (gamma-benzenehexachloride; gamma-BHC) on GABA-evoked Cl- current (IGABA) in freshly dissociated frog sensory (dorsal root ganglion) neurons were studied and compared with those of tert-butylbicycloortho benzoate (TBOB) and picrotoxin by the use of the suction-pipette method [13]. Drugs were applied with a rapid drug-application method, "Concentration-clamp" technique. At concentration of GABA of > 3 x 10(-6) M, at least two components of the IGABA were recognized distinct degree of desensitization. Those were defined as the peak and plateau components in the text. At low concentration (3 x 10(-7) M) of gamma-BHC, only the plateau component of IGABA at 10(-5) M were depressed without changing the peak amplitude. While gamma-BHC at high concentration (3 x 10(-5) M) depressed both the peak and plateau current components. The gamma-BHC-induced depression of IGABA seemed to be IGABA-component-dependent. A detailed analysis of the gamma-BHC action in the concentration-response relationship for GABA revealed that the IGABA with strong desensitization was preferentially blocked by gamma-BHC (3 x 10(-5) M). The rate of recovery of the IGABA from gamma-BHC-induced block depended on the concentration of GABA. The lower the concentration of GABA, the slower the recovery. The GABAA receptor Cl- channels were proposed to be classified into two types of the gamma-BHC-sensitive and -resistant ones.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Physiological roles of glycine and gamma-aminobutyric acid in dissociated neurons of rat visual cortex.

The effects of glycine (Gly) and gamma-aminobutyric acid (GABA) on the neurons acutely dissociated from rat visual cortex (VC) were investigated in the whole-cell mode using a conventional patch-clamp technique. GABA and Gly evoked Cl- currents (ICl) in a concentration-dependent manner at a holding potential (VH) of -50 mV. The half maximum effective concentrations (EC50) were 4.64 x 10(-6) M for GABA and 6.67 x 10(-5) M for Gly. Strychnine and bicuculline reversively inhibited both 10(-5) M GABA- and 10(-4) M Gly-induced ICl in a concentration-dependent manner. The half maximum inhibitory concentrations (IC50) of strychnine on GABA- and Gly-induced currents were 4.00 x 10(-6) M and 8.26 x 10(-8) M, respectively. The IC50 values of bicuculline on GABA and Gly responses were 1.18 x 10(-6) M and 2.97 x 10(-4), respectively. GABA at 10(-5) M, which is near the EC50 of the GABA response, induced ICl in all neurons tested (n = 83). However, Gly of 10(-4) M, which is also near the EC50 of the Gly response, induced ICl in 34 out of 83 neurons tested (41%). Moreover, the maximum amplitude of the Gly response was about 60% of that of the GABA response. On the other hand, the enhancement of N-methyl-D-aspartate (NMDA, 3 x 10(-4) M) response by Gly (10(-6) M) was observed in all neurons (n = 36) whether they had the Gly-induced ICl or not.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Metabotropic glutamate response in acutely dissociated hippocampal CA1 pyramidal neurones of the rat.

1. The metabotropic glutamate (mGlu) response was investigated in dissociated rat hippocampal CA1 pyramidal neurones using conventional and nystatin-perforated whole-cell modes of the patch recording configuration. 2. In the perforated patch recording configuration, the application of glutamate (Glu), quisqualate (QA), aspartate (Asp) and N-methyl-D-aspartate (NMDA) induced a slow outward current superimposed on a fast ionotropic inward current, whereas alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) and kainate (KA) induced only an ionotropic inward current at a holding potential (VH) of -20 mV. A specific agonist of the mGlu receptor (mGluR), trans-1-aminocyclopentane-1,3-dicarboxylate (tACPD), induced an outward current in approximately 80% of the neurones tested. Asp- and NMDA-induced outward currents were antagonized by D-2-amino-5-phosphonopentanoate (D-AP5) whereas Glu-, QA- and tACPD-induced outward currents were not antagonized by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), 6,7-dinitroquinoxaline-2,3-dione (DNQX) and D-AP5, indicating that the mGlu response is an outward current component. 3. L-2-Amino-3-phosphonopropionate (L-AP3) and DL-2-amino-4-phosphonobutyrate (AP4) did not block the mGlu response. 4. The relative potencies of mGlu agonists were QA > Glu > tACPD. The threshold and EC50 values of metabotropic outward currents were 10-100 times lower than those of the ionotropic inward current (iGlu response). 5. The reversal potential of the mGlu response (EmGlu) was close to EK (K+ equilibrium potential), and it shifted 59.5 mV for a tenfold change in extracellular K+ concentration. 6. In Ca(2+)-free external solution, the mGlu response was elicited by an initial application of Glu, but subsequent applications failed to induce the response. There was also an increase in the intracellular free Ca2+ concentration ([Ca2+]i) during the application of Glu and QA but not of AMPA, indicating Ca2+ release from an intracellular Ca2+ store. 7. During the activation of a Ca(2+)-dependent K+ current (IK(Ca)) by inositol trisphosphate (IP3) in the internal solution, the mGlu response was suppressed. Addition of GDP-beta-S, neomycin or heparin to the internal solution also suppressed the mGlu response, but staurosporine had no effect. The mGlu response was abolished by pretreatment with either caffeine or ryanodine, but treatment with pertussis toxin (IAP) for 6-8 h had no effect. 8. The mGlu response was suppressed by tetraethylammonium, but not by either apamin or iberiotoxin, suggesting that intermediate-conductance Ca(2+)-dependent K+ (KCa+) channels are involved.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1994

Nicotinic and muscarinic acetylcholine responses in differentiated PC12 cells.

Nicotinic and muscarinic acetylcholine (ACh) responses were investigated in PC12 cells using the conventional whole-cell and nystatin perforated patch techniques. With the nystatin perforated patch, ACh induced three kinds of ionic currents: a rapid transient inward current, a subsequent transient outward current and a long-lasting slow inward current, whereas only a transient inward current was recorded by conventional whole-cell patch. The transient rapid inward current was mimicked by nicotine, but not by muscarine. On the contrary, the transient outward current and the long-lasting slow inward current were mimicked by muscarine but not by nicotine. Both nicotinic and muscarinic antagonists inhibited the transient inward current and the subsequent outward current in a concentration-dependent manner. The current-voltage relationship for the nicotine-induced transient current showed an inward rectification and the reversal potential was close to the Na+ equilibrium potential. The ACh-, muscarine-, CCh- and oxotremorine-M induced outward currents increased in a sigmoidal fashion with an increase in the concentration. Neither McN-A-343, an M1 agonist, nor oxotremorine, an M2 agonist, mimicked the muscarinic response. The reversal potential of the muscarinic response was close to the K+ equilibrium potential. The muscarinic response was not affected by pre-treatment with pertussis toxin but was enhanced by pre-treatment with Li+. In the cells perfused with Ca(2+)-free external solution, only the first application of ACh induced the muscarinic response. Calmodulin antagonists reversibly blocked the muscarinic response in a concentration-dependent manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗

PubMed1994

Facilitatory effect of docosahexaenoic acid on N-methyl-D-aspartate response in pyramidal neurones of rat cerebral cortex.

1. The effect of docosahexaenoic acid (DHA) on N-methyl-D-aspartic acid (NMDA) responses in the presence of glycine was investigated in pyramidal neurons acutely dissociated from rat cerebral cortex in whole-cell and single channel configurations. 2. DHA potentiated the NMDA-induced response but reduced the non-NMDA (kainate-induced) response in a concentration-dependent manner at a holding potential of -60 mV under voltage-clamp conditions. 3. Arachidonic acid (AA) also potentiated the NMDA-induced response in a manner similar to DHA. Oleic acid caused a slight potentiation. However, other polyunsaturated and saturated fatty acids had no such effects. 4. The facilitatory action of DHA on the NMDA-induced response was not affected by adding inhibitors of cyclo-oxygenase, lipoxygenase or phospholipase A2, suggesting that DHA may exert its facilitatory effect directly on the NMDA receptor. 5. The facilitatory action of DHA was observed in the presence of a saturating dose of NMDA. Moreover, a detailed analysis of the NMDA receptor-operated single channel currents revealed that, in the presence of DHA, the open probability of the channel increased without changing the conductance, indicating that DHA may act by binding directly to a novel site on the NMDA receptor or by altering the lipid environment of the NMDA receptor and thereby potentiating the response to NMDA. 6. The results are discussed in terms of the possibility that DHA may play an important role in the genesis of long-term potentiation, at least that involving the activation of NMDA receptors.

Animals↗

PubMed1994

Voltage-dependent channels in dissociated outer hair cells of the guinea pig.

Voltage-dependent channels in outer hair cells (OHCs) dissociated from the guinea pig cochlea were investigated by the use of a whole-cell patch-clamp technique. Two types of K+ current were recorded from OHCs. One was a slowly inactivating K+ current that was activated at a potential more positive than -30 mV. Another is a K+ current that was already activated at resting membrane potential. After suppressing both K+ currents, depolarizing voltage steps elicited a slowly inactivating inward current that was dependent on external Ca2+ and was indicative of an L-type Ca2+ channel in OHCs. Aminoglycoside antibiotics known to be ototoxic selectively inhibited the Ca2+ current.

Aminoglycosides↗