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N Akaike

Publications and source records attributed to N Akaike.

At least 163 records · Page 9Linked to original sources
PubMed1994

Intracellular Na+ and K+ shifts induced by contractile activities of rat skeletal muscles.

The effects of direct and indirect electrical stimulation on intracellular potassium and sodium contents ([K]i and [Na]i, respectively) in rat soleus muscle (SOL) and extensor digitorum longus muscle (EDL) were investigated under in vivo conditions. The changes of [K]i and [Na]i contents in both muscles which were stimulated indirectly reached respective values at 30 min or 1 hr after the beginning of stimulation, whereas those of EDL stimulated with 60 Hz changed gradually through 2 hr stimulation. The shifts of [K]i and [Na]i in EDL occurred during the twitch contraction at considerably lower frequency stimulation (0.5-10 Hz), whereas those in SOL were observed during the tetanus contraction at high frequency stimulation (10-40 Hz). The difference of change in cationic shifts between EDL and SOL under low frequency stimulation was reduced by ouabain treatment, though the difference was still significant. When the muscles were indirectly stimulated 6000 times at 1, 5, 10 and 20 Hz, the cationic shifts in EDL were greater than those in SOL, extending over all frequencies. It was concluded that such a difference in ionic shift between contracting EDL and SOL may be primarily due to the difference in unidirectional ionic fluxes per stimulation and, secondly, to the difference in Na(+)-K+ pump activity.

Animals↗
PubMed1994

Muscarinic acetylcholine response in pyramidal neurones of rat cerebral cortex.

1. The effects of acetylcholine (ACh) on pyramidal neurons acutely dissociated from the rat cerebral cortex were studied in the whole-cell mode, by use of the nystatin-perforated patch recording configuration. 2. ACh induced a net inward current (IACh) accompanied by a membrane conductance decrease at a holding potential (VH) of -40 mV. IACh increased in a concentration-dependent manner with a half-maximum concentration (EC50) of 8.7 x 10(-7) M. 3. IACh mainly resulted from the suppression of the voltage- and time-dependent K+ current (M-current). 4. Muscarine and muscarinic agonists such as McN-A-343, oxotremorine and oxotremorine-M mimicked the ACh response. The potency was in the order of oxotremorine-M > McN-A-343 > or = muscarine > oxotremorine. 5. Pirenzepine shifted the concentration-response curve for ACh to the right and the corresponding Schild plot yielded a pA2 value of 7.81. Other muscarinic antagonists also reversibly blocked IACh in a concentration-dependent manner. The inhibitory potency was in the order of atropine > 4-DAMP > pirenzepine > AF-DX-116. 6. IACh could be induced normally even after pre-incubation of dissociated neurones in external solution with 200 ng ml-1 pertussis toxin (PTX) for 8 h, whereas the inhibitory effect of ACh on high-voltage-activated Ca2+ channels was completely abolished by the PTX treatment.

Acetylcholine↗
PubMed1994

Suramin and reactive blue 2 are antagonists for a newly identified purinoceptor on rat megakaryocyte.

1. The effects of purinoceptor antagonists on ATP-induced oscillatory K(+)-currents in rat isolated megakaryocytes were investigated. 2. Both reactive blue-2 (RB-2), a selective antagonist of the P2Y purinoceptor, purinoceptor, at concentrations of 0.3-10 microM and suramin, a non-selective P2 purinoceptor antagonist, at 1-30 microM blocked the ATP-induced oscillation in a concentration-dependent manner. 3. RB-2 and suramin also blocked the ADP-induced K(+)-current oscillation at the same concentration range as in the case of ATP. However, both suramin and RB-2 had no effect on thrombin- and inositol 1,4,5-trisphosphate (IP3)-induced K+ current oscillation, indicating that they act as specific purinoceptor antagonists. 4. Thus, the purinoceptors on megakaryocytes show the properties of the P2 subtype according to their blockade by antagonists.

Adenosine Diphosphate↗
PubMed1994

ATP-induced inward current in neurons freshly dissociated from the tuberomammillary nucleus.

1. Neurons in the tuberomammillary nucleus (TMN), which are considered to be histaminergic, were dissociated and their response to extracellularly applied ATP was investigated in the nystatin-perforated patch recording mode under voltage-clamp condition. 2. ATP induced a sustained inward current that was slowly desensitized at a holding potential of -60 mV. 3. The ATP response increased in a concentration-dependent manner. The half-maximum concentration (EC50) was 44 microM and the Hill coefficient was 1.8. 4. The potency of ATP analogues was in the order of ATP > or = 2-methylthio-ATP >> alpha, beta-methylene ATP > or = ADP. Neither adenosine nor AMP induced any response. The results suggest that the purinergic receptor in TMN neurons is P2y. 5. The current-voltage relationship for the 100 microM ATP showed a significant inward rectification at a potential more positive than -20 mV in an external solution with 150 mM Na+, but a significant rectification current was not observed in an external solution with 150 mM Cs+. The change in the reversal potential of the ATP response (EATP) to a 10-fold change of extracellular Na+ concentration was 56 mV, indicating that the ATP-induced current is highly selective for Na+ over Cl-. 6. The permeability ratio for cations was Na+:Li+:K+:Rb+: Cs+:Ca2+ = 2.16:1.36:1.68:1.54:1:2.55, indicating that the ATP-induced current is passing through the ligand-gated nonselective cation channel. 7. These results suggest that ATP has an excitatory effect on the TMN neurons by opening nonselective cation channels.

Adenosine Triphosphate↗
PubMed1994

Gramicidin perforated patch-clamp technique reveals glycine-gated outward chloride current in dissociated nucleus solitarii neurons of the rat.

1. The inhibitory response of exogenously applied glycine was investigated in freshly dissociated rat nucleus tractus solitarii neurons under whole cell configuration using new perforated patch-clamp technique termed "gramicidin perforated patch technique," which maintains intact intracellular Cl- concentrations. 2. Using the gramicidin perforated patch technique, at a holding potential (VH) of -45 mV, glycine induced outward currents in a concentration-dependent manner with a EC50 of 4.0 x 10(-5) M and at a Hill coefficient of 1.5. In contrast, using the nystatin perforated patch technique, glycine induced inward currents at the same VH in a concentration-dependent manner with an EC50 of 4.9 x 10(-5) M and at a Hill coefficient of 1.2. 3. The glycine-induced outward currents were blocked by strychnine in a concentration dependent manner with an IC50 of 2.2 x 10(-8) M. The blockade was competitive. 4. The current-voltage relationship for the 10(-5) M glycine response showed a clear outward rectification. 5. Ten-fold change of extracellular Cl- with a large impermeable anion resulted in a 65 mV shift of the reversal potential of glycine-induced currents (EGly), indicating that the membrane behaves like a Cl- electrode in the presence of glycine. 6. The intracellular Cl- activity calculated from the EGly ranged from 7.3 to 18.2 mM, with a mean value of 13.3 mM. 7. The values of EGly in the individual neurons were significantly negative to the resting membrane potentials, suggesting the existence of active transport of Cl-.

Animals↗
PubMed1994

Glycine response in acutely dissociated ventromedial hypothalamic neuron of the rat: new approach with gramicidin perforated patch-clamp technique.

1. We investigated the glycine-induced response in ventromedial hypothalamic (VMH) neurons freshly dissociated from 8- to 12-day-old rats using the nystatin and gramicidin perforated patch recording modes. The nystatin-formed pores in the plasma membrane are permeable for both monovalent cations and anions, whereas those formed by gramicidin are permeable only to monovalent cations. Therefore, when the patch-pipette contains 150 mM Cl- and gramicidin, the physiological intracellular Cl- concentration ([Cl-]i) is undisturbed in the cell-attached condition of the pipette. 2. At holding potentials of -40 to -60 mV, glycine induced inward currents and outward currents in the nystatin and gramicidin perforated patch recording modes, respectively. The values of the half-maximum effective concentration (EC50) and the Hill coefficient in the concentration-response relationships of the glycine responses were 2.9 x 10(-5) M, 1.1, and 4.2 x 10(-5) M, 1.4, respectively. These values were quite similar in both recording modes. 3. The reversal potentials of the glycine responses (EGly) were -1.5 mV in the nystatin perforated patch recording and -75.0 to -24.8 mV in the gramicidin perforated patch recording. 4. Strychnine (3 x 10(-8) M) inhibited the glycine-induced outward currents in a competitive manner and the half-inhibition concentration (IC50) of strychnine on the 10(-4) M glycine-induced response was 1.9 x 10(-8) M. 5. The physiological [Cl-]i in the VMH neurons calculated from the EGly obtained by the gramicidin perforated patch mode ranged from 6.0 to 43.8 mM (n = 28).

Animals↗
PubMed1994

3-O-methyldopa attenuates the effects of Madopar on the haloperidol-induced cataleptic behavior and the locomotor activity in the mouse.

The effects of Madopar (levodopa plus benserazide) on the cataleptic behavioral response to haloperidol and on the locomotor activity in mice were quantitatively compared before and after the administration of 3-O-methyldopa (3OMD). The intraperitoneal administration of 3OMD (200-400 mg/kg) alone did not modify the haloperidol (1.0 mg/kg s.c.)-induced catalepsy. Madopar, depending on the dose regimen, markedly antagonized the haloperidol-induced catalepsy. Pretreatment with 3OMD tended to reverse the antagonistic property of Madopar on the cataleptic behavior in response to haloperidol. The ability of 3OMD to significantly inhibit Madopar effects was observed in the locomotor testing paradigm; the locomotor hyperactivity in Madopar-treated animals was significantly inhibited by a prior intraperitoneal injection of 3OMD. The results from our animal experiments may provide further evidence that impediment of 3OMD formation is meaningful in the treatment of Parkinson's disease with Madopar or levodopa.

Animals↗
PubMed1994

Nystatin perforated patch recording and its applications to analyses of intracellular mechanisms.

We have reviewed the basic aspects of history, physicochemical properties, advantages, disadvantages, and applications of nystatin- and amphotericin B-perforated patch recording. Recently, we have developed a novel perforated patch technique using gramicidin [49, 132, 133]. Since gramicidin pores are permeable to Na+ and K+ but not to Cl-, it is possible to maintain the physiological concentration of intracellular Cl- and thereby to measure it in real-time from small neurons. Further improvement of the perforated patch techniques would be possible by limiting redistribution of specific intracellular ions. In light of their broad applicability, the perforated patch techniques will prove indispensable for electrophysiologists working on the functions and modulations of receptors, ion channels and transport phenomena. Research with the perforated patch should continue to provide important information relevant to the physiological and pathological conditions of cells.

Animals↗
PubMed1994

Glycine responses in rat CNS neurons studied with gramicidin perforated patch recording.

The conventional whole-cell recording of the patch-clamp technique has a great advantage over other electrical recording methods in that it could perfectly control the extra- and intracellular concentrations of ions (such as Na+, K+, Ca2+, and Cl-). However, this advantage is a two-edged sword: it disrupts the physiological ionic environment inside cells. Thus, various Cl(-)-mediated responses in neurons, such as those elicited by inhibitory amino acids, gamma-amino butyric acid (GABA) and glycine (Gly), have been recorded only under an artificial condition. Subsequently, measurement of the normal concentration of intracellular Cl- ([Cl-]i) has been much hampered. [Cl-]i is suggested to play a role in membrane excitability (Deisz and Lux: J Physiol 326: 123-138, 1982) and intracellular signal transduction (Higashijima, Ferguson, and Sternweis: J Biol Chem 262: 3597-3602, 1987), yet the detailed analysis of these fundamental roles has been left undone due to technical difficulties. We have recently developed a "gramicidin perforated patch recording", a novel method of patch-clamp technique that enables analysis of membrane currents with intact [Cl-]i. We here report that by applying this method to acutely dissociated CNS neurons of the rat, we could analyze the Gly-induced membrane currents in the normal ionic environment. And using the reversal potentials, we could deduce the actual [Cl-]i of central neurons.

Animals↗
PubMed1993

Nystatin-perforated patch recordings disclose KA-operated outward currents in rat cortical neurons.

Kainate (KA)-induced responses were studied in acutely dissociated rat cortical neurons. KA elicited the inward currents with conventional whole-cell and nystatin-perforated patch recordings under voltage-clamp condition. An additional outward current was observed only with the perforated patch recording. The outward current was due to the activation of K+ current by Ca2+ passing through the KA channels. This K+ channel was sensitive to both iberiotoxin and tetraethylammonium (TEA)-Cl. This K+ channel may serve to limit the depolarization during excessive KA-mediated excitation.

Animals↗
PubMed1993

Alterations of Ca2+ currents and their sensitivities to Ca2+ antagonists during application and after deprivation of nerve growth factor.

The alterations in morphology and Ca2+ currents (ICa) were assessed in PC12 cells, which were (1) control (untreated), (2) treated with nerve growth factor (NGF), and (3) deprived of NGF. NGF treatment induced neuronal differentiation morphologically and increased the current density of ICa, and especially that of the omega-conotoxin (omega-CgTX)-sensitive component. NGF-deprived cells manifested morphological deterioration and did not exhibit remarkable changes in the current density of the total ICa and dihydropyridine components, whereas the omega-CgTX-sensitive ICa component was decreased significantly compared with that in NGF-treated cells. The results suggest that the total function of Ca2+ channels, including the dihydropyridine component, does not seem to be lost at the initial stage of neuronal deterioration, whereas omega-CgTX-sensitive Ca2+ channels lost their function early.

Animals↗
PubMed1993

Cytoplasmic pH regulates ATP-induced Ca(2+)-dependent K(+)-current oscillation in rat megakaryocytes.

The effect of cytoplasmic pH (pH(i)) on ATP-induced Ca2+ oscillation of rat megakaryocytes was investigated by the whole-cell patch-clamp technique. Megakaryocytes responded to extracellular ATP and showed the periodic activation of K+ channels, which reflects the oscillation in intracellular free Ca2+ concentration. Intracellular alkalinization by 20 mM NH4Cl resulted in inhibition of the oscillatory response, and intracellular acidification by 20 mM sodium acetate enhanced the response. NH4Cl also inhibited the Ins(1,4,5)P3-induced oscillation. Sodium acetate had no effect on the InsP3-induced oscillation, but enhanced the guanosine 5'-[gamma-thio]triphosphate-induced response. These results indicate that pH(i) modulates the ATP-induced cellular response at least at two points.

Acetates↗