Details of a Researcher - Takahashi, Shinichi

Papers - Takahashi, Shinichi

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糖尿病と神経系　脳の糖代謝と脳循環

高橋, 慎一 and 福内, 靖男

Clinical Neuroscience 14 ( 12 ) 1353 - 1356 1996.12

ISSN 0289-0585

Contribution of astroglia to functionally activated energy metabolism

Sokoloff, L., Takahashi, S., Gotoh, J., Driscoll, B. F. and Law, M. J.

Dev Neurosci 18 ( 5-6 ) 344 - 52 1996

ISSN 0378-5866

Studies of local glucose utilization in neural tissues in vivo with the autoradiographic [14C]deoxyglucose method have demonstrated that energy metabolism increases almost linearly with the degree of functional activation, i.e. spike frequency, in the terminal projection zones of activated pathways. The increased metabolism is found in neuropil and is minimal or undetectable in neuronal cell bodies. Electrical stimulation, increased extracellular [K+] ([K+]o), or opening of Na+ channels with veratridine stimulates metabolism in neutral tissues, and this increase is blocked by ouabain, a specific inhibitor of Na+,K(+)-ATPase. Activation of this enzyme to restore ionic gradients across cellular membranes appears to mediate the function-related increase in energy metabolism. The metabolic activation is, therefore, not directly related to the functional activity itself but to processes operating to recover from that activity. The limited spatial resolution of the [14C]DG method precludes identification of cellular elements in neuropil participating in the metabolic activation, e.g. axonal terminals, dendrites, or astrocytic processes enveloping the synapses. We have, therefore, attempted to stimulate in vitro conditions to be expected from functional activation and increased spike activity in vivo, e.g. increased extracellular [K+], intracellular [Na+], or extracellular neurotransmitter levels, and examined their effects on glucose metabolism in neurons and astroglia in culture. Increased [K+]o stimulated [14C]DG phosphorylation in neuronal and mixed neuronal-astroglial cultures, but not in astroglial cultures assayed in bicarbonate buffer; it did occasionally stimulate metabolism in astroglia when assayed in HEPES or phosphate buffers, but these effects were variable and inconsistent. Veratridine (75 microM) stimulated [14C]DG phosphorylation in neurons and astroglia; these stimulations were blocked by 1 mM ouabain or 10 microM tetrodotoxin (TTX), which blocks voltage-dependent Na+ channels. The Na+ ionophore monensin (10 microM) doubled the rate of metabolism, a stimulation that was only partially blocked by ouabain and unaffected by TTX. L-Glutamate (500 microM) stimulated [14C]DG phosphorylation in astroglia, but this stimulation was probably secondary to Na+ uptake into the cells via a sodium/glutamate co-transporter because it was not blocked by inhibitors of NMDA or non-NMDA receptors but was absent in Na(+)-free medium. These results indicate that astroglia contribute to the increased energy metabolism in neuropil during functional activation by mechanisms that promote Na+ entry into the cells.

Lack of effects of inhibition of nitric oxide synthesis on local glucose utilization in the rat brain

Takahashi, S., Cook, M., Jehle, J., Kennedy, C. and Sokoloff, L.

J Neurochem 65 ( 1 ) 414 - 9 1995.07

ISSN 0022-3042

The effects of chronic treatment with NG-nitro-L-arginine methyl ester, a potent inhibitor of nitric oxide synthase activity, on local cerebral glucose utilization were examined in conscious rats. Intraperitoneal injections of 50 mg/kg of the nitroarginine twice daily for 4 days have been found to result in almost complete inhibition of nitric oxide synthase activity in brain. Local cerebral glucose utilization was determined by means of the quantitative autoradiographic [14C]deoxyglucose method in an experimental group (n = 7) of rats that were treated with the nitroarginine according to this schedule and in a normal control group (n = 7) treated similarly with saline. The rats were conscious but partially restrained during the determinations of local cerebral glucose utilization. The nitroarginine treatment raised mean arterial blood pressure statistically significantly to 147 +/- 3 mm Hg (mean +/- SEM) from a level of 120 +/- 5 mm Hg in the saline controls (p < 0.001 by grouped t test), but there were no statistically significant effects on glucose utilization in any of 39 brain structures examined. It is concluded that nitric oxide normally exerts no significant influence on energy metabolism in the rat brain.

Role of sodium and potassium ions in regulation of glucose metabolism in cultured astroglia

Takahashi, S., Driscoll, B. F., Law, M. J. and Sokoloff, L.

Proc Natl Acad Sci U S A 92 ( 10 ) 4616 - 20 1995.05

ISSN 0027-8424

Effects of increasing extracellular K+ or intracellular Na+ concentrations on glucose metabolism in cultures of rat astroglia and neurons were examined. Cells were incubated in bicarbonate buffer, pH 7.2, containing 2 mM glucose, tracer amounts of [14C]deoxyglucose ([14C]dGlc), and 5.4, 28, or 56 mM KCl for 10, 15, or 30 min, and then for 5 min in [14C]dGlc-free buffer to allow efflux of unmetabolized [14C]dGlc. Cells were then digested and assayed for labeled products, which were shown to consist of 96-98% [14C]deoxyglucose 6-phosphate. Increased K+ concentrations significantly raised [14C]deoxyglucose 6-phosphate accumulation in both neuronal and mixed neuronal-astroglial cultures at 15 and 30 min but did not raise it in astroglial cultures. Veratridine (75 microM), which opens voltage-dependent Na+ channels, significantly raised rates of [14C]dGlc phosphorylation in astroglial cultures (+20%), and these elevations were blocked by either 1 mM ouabain, a specific inhibitor of Na+,K(+)-ATPase (EC 3.6.1.37), or 10 microM tetrodotoxin, which blocks Na+ channels. The carboxylic sodium ionophore, monensin (10 microM), more than doubled [14C]dGlc phosphorylation; this effect was only partially blocked by ouabain and unaffected by tetrodotoxin. L-Glutamate (500 microM) also stimulated [14C]dGlc phosphorylation in astroglia--not through N-methyl-D-aspartate or non-N-methyl-D-aspartate receptor mechanisms but via a Na(+)-dependent glutamate-uptake system. These results indicate that increased uptake of Na+ can stimulate energy metabolism in astroglial cells.

Preservation of autoregulatory cerebral vasodilator responses to hypotension after inhibition of nitric oxide synthesis

Takahashi, S., Cook, M., Jehle, J., Kennedy, C. and Sokoloff, L.

Brain Res 678 ( 1-2 ) 21 - 8 1995.04

ISSN 0006-8993

Effects of inhibition of nitric oxide (NO) synthesis on the cerebrovascular autoregulatory vasodilator response to hypotension were studied in conscious rats. Cerebral blood flow (CBF) was determined with [14C]iodoantipyrine in a saline-treated control group and in three groups following inhibition of NO synthase activity by twice daily intraperitoneal injections of 50 mg/kg of NG-nitro-L-arginine methyl ester (L-NAME) for four days. In the saline-control group (n = 8) and in the L-NAME-treated Group (a) (n = 8) CBF was determined while systemic mean arterial blood pressure (MABP) remained at its resting level (means +/- S.D., 128 +/- 6 and 151 +/- 11 mmHg, respectively). In the other groups CBF was determined after MABP was reduced by blood withdrawal to 118 +/- 9 and 88 +/- 8 mmHg in Groups (b) (n = 8) and (c) (n = 8), respectively. Despite the elevated MABP, global CBF was significantly lower in L-NAME-treated Group (a) than in the saline-controls (P < 0.005), indicating cerebral vasoconstriction resulting from inhibition of NO synthesis. Global CBF was not significantly reduced further in the two groups with hypotension. Local CBF in the hypotensive rats showed no significant reductions below values in L-NAME-treated control rats (Group (a)) in 31 of 32 brain structures; the only exception was in the auditory cortex of the severely hypotensive rats (Group (c)). The autoregulatory mechanism for cerebral vasodilatation to compensate for reduced arterial blood pressure is maintained following inhibition of NO synthesis.

Role of the cerebellar fastigial nucleus in the physiological regulation of cerebral blood flow

Takahashi, S., Crane, A. M., Jehle, J., Cook, M., Kennedy, C. and Sokoloff, L.

J Cereb Blood Flow Metab 15 ( 1 ) 128 - 42 1995.01

ISSN 0271-678X

Local cerebral blood flow (ICBF) was measured with [14C]iodoantipyrine in conscious, unrestrained rats during electrical stimulation of the fastigial nucleus (FN). Electrode position in the FN was determined by blood pressure (MABP) responses to stimulation under anesthesia. In nine rats in which MABP responses had been variable under anesthesia, bipolar stimulation (50 Hz, 0.5 ms, 1 s on/1 s off) with currents of 30-100 microA after recovery from anesthesia produced stereotypic behavior but little effect on MABP and ICBF. In seven other conscious rats currents could be raised to 75-200 microA without inducing seizures, resulting in sustained MABP elevations during the ICBF measurement and significantly increased ICBF in the sensory-motor (+45%), parietal (+31%), and frontal cortices (+56%) and the caudate-putamen (+27%) above control values (n = 9). Glucose utilization, measured with [14C]deoxyglucose, in rats similarly stimulated was significantly increased in six structures, including some of the above, indicating increases in ICBF due to metabolic activation. Unilateral or bilateral electrolytic lesions of the FN, placed 6-7 days before ICBF measurement, had negligible effects on resting ICBF and on autoregulation in conscious rats. These results fail to support a specific role for the FN in physiological regulation of cerebral blood flow in unanesthetized rats.

Access to Document (DOI)

Increases in local cerebral blood flow associated with somatosensory activation are not mediated by NO

Adachi, K., Takahashi, S., Melzer, P., Campos, K. L., Nelson, T., Kennedy, C. and Sokoloff, L.

Am J Physiol 267 ( 6 Pt 2 ) H2155 - 62 1994.12

ISSN 0002-9513

Effects of inhibition of nitric oxide (NO) synthase by NG-nitro-L-arginine methyl ester (L-NAME) on the increases in local cerebral blood flow (LCBF) produced in the whisker-to-barrel sensory pathway by vibrissal stimulation were studied in conscious rats with the autoradiographic iodo[14C]antipyrine method. Unilateral whisker stroking increased LCBF in the ipsilateral trigeminal spinal and principal sensory nuclei, contralateral ventral posteromedial thalamic nucleus, and contralateral somatosensory barrel cortex. Intravenous L-NAME (30 mg/kg) lowered baseline LCBF without altering the percent increases due to stimulation. Intracisternal infusions of L-NAME in doses about 10 times the molar content of free arginine in brain inhibited brain NO synthesis activity by 88%, but the percent augmentations of LCBF by stimulation remained unchanged. Chronic treatment with L-NAME (50 mg/kg ip twice daily for 4 days) inhibited NO synthase activity in brain by 84% but also failed to reduce the percent increases in LCBF due to stimulation. These results indicate that NO does not mediate the increases in LCBF associated with functional activation.

Locus coeruleus stimulation exerts different influences on the dynamic changes of cerebral pial and intraparenchymal vessels

Ohta, K., Gotoh, F., Shimazu, K., Amano, T., Komatsumoto, S., Hamada, J. and Takahashi, S.

Neurol Res 13 ( 3 ) 164 - 7 1991.09

ISSN 0161-6412

The present experimental study was undertaken to investigate the effects of locus coeruleus stimulation on the dynamic changes of intraparenchymal vessels and pial vessels. Twelve cats were anaesthetized with alpha-chloralose and urethane. For stimulation of the locus coeruleus, a concentric stainless-steel needle electrode was inserted stereotaxically. During the stimulation, volumetric changes of the intraparenchymal vessels were monitored by a photoelectric method for estimating the cerebral blood volume (CBV) (6 cats), and the diameters of pial arteries were measured continuously using a video camera system (6 cats). The CBV followed a decreasing course during the stimulation of the locus coeruleus. The decrease in CBV from the control value (6.3 vol%) was 0.14 +/- 0.04 vol% at 80 s (p less than 0.05), 0.15 +/- 0.05 vol% at 100 s (p less than 0.05), and 0.15 +/- 0.03 vol% at 120 s (p less than 0.01). After cessation of the stimulation, CBV showed a gradual recovery. On the other hand, the diameters of the pial arteries did not change during or after the stimulation of the locus coeruleus. The above results suggest that the locus coeruleus has a vasoconstrictive effect on the intraparenchymal vessels, although it exerts no apparent influence on the pial arteries.

クモ膜下出血(SAH)における上頸部交感神経節節前線維の電気活動

高橋, 慎一

自律神経 27 ( 3 ) 338 - 345 1990.06

ISSN 0288-9250

SAH後の脳血管攣縮に対するノルアドレナリン(NA)作動性神経系の関与を明らかにするため,実験的SAHにおける上頸部交感神経節(SCG)節前線維の電気活動を検討した.成猫13匹を用い,SCG近傍で節前線維を切断後,中枢側から活動電位を導出し,pulse density variation法を用いて連続的に解析した.実験的SAHは大槽内に自家血0.3 mlを注入し作製した(SAH群8例),対照群(5例)では生理食塩水0.3 mlを注入をした.SAH群では節前線維の放電頻度はSAH作製後,前値に比し有意に増加した(10分後:186.9±48.1%,mean±SEM, 30分後:328.4±88.5%,90分後:296.3±132.0%,各々p<0.05),対照群の放電頻度は有意な変化を示さなかった.なお,経過中両群とも全身血圧に有意な変動を認めなかった.SAH急性期において,脳軟膜血管壁に分布するNA作動性神経系の電気活動亢進が示唆された

青斑核が脳実質内血管に及ぼす収縮作用に関する研究

高橋, 慎一, 後藤, 文男, 島津, 邦男 and 他

自律神経 26 ( 4 ) 394 - 400 1989.08

ISSN 0288-9250

青斑核の脳実質内血管に対する作用について

高橋, 慎一 and 他

自律神経 26 ( 2 ) 200 1989.04

ISSN 0288-9250

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