• Toxicological Research
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• 제16권1호
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• pp.63-66
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• 2000

The effects of acute ethanol on the high K+ induced $Ca^{2+}}$ signals were examined from primary cultures of cerebellar granule neurons. $Ca^{2+}}$ signals were measured with Calcium Green-1 based microscopic video imaging. Because $Ca^{2+}}$ signal was low in most of granule neurons without stimuli, high KCI was used for depolarization. In most case, acute exposure to ethanol reduced the peak amplitude of the $Ca^{2+}}$ signals, induced by high K+, even though low concentration of ethanol(2~10mM) was used and the effects lasted more than 30min. In was also possible to see differences of ethanol inhibition, i.e. the temporal pattern of $Ca^{2+}}$ signal reductions and the strength of inhibition of $Ca^{2+}}$ signals in cerebellar granule neurons. These results indicate that low concentration of ethanol has diverse actions on the $Ca^{2+}}$ signals in cerebellar granule neurons.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 2004년도 Annual Meeting of the Korean Society ofApplied Pharmacology
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• pp.124-128
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• 2004

We have assessed amyloid ${\beta}-peptide$ $(A{\beta})-induced$ neurotoxicity in primary neurons and organotypic hippocampal slice cultures (OHC) in rat. Exposing cultured hippocampal and cerebellar granule neurons to $A{\beta}$ resulted in a decrease of MTT reduction, and in destruction of neuronal integrity. Treatment of these neurons with tunicamycin, an inhibitor of N-glycosylation in the endoplasmic reticulum (ER), also decreased MTT reduction in these neurons. S-allyl-L-cysteine (SAC), an active organosulfur compound in aged garlic extract, protected hippocampal but not cerebellar granule neurons against $A{\beta}$- or tunicamycin-induced toxicity. In the hippocampal neurons, protein expressions of casapse-12 and GRP 78 were significantly increased after $A{\beta}_{25-35}$ or tunicamycin treatment. The increase in the expression of caspase-12 was suppressed by simultaneously adding $1{\mu}M$ SAC in these neurons. In contrast, in the cerebellar granule neurons, the expression of caspase-12 was extremely lower than that in the hippocampal neurons, and an increase in the expression by $A{\beta}_{25-35}$ or tunicamycin was not detected. In OHC, ibotenic acid (IBO), a NMDA receptor agonist, induced concentration-dependent neuronal death. When $A{\beta}$ was combined with IBO, there was more intense cell death than with IBO alone. SAC protected neurons in the CA3 area and the dentate gyrus (DG) from the cell death induced by IBO in combination with $A{\beta}$, although there was no change in the CA1 area. Although protein expression of casapse-12 in the CA3 area and the DG was significantly increased after the simultaneous treatment of AI3 and IBO, no increase in the expression was observed in the CA1 area. These results suggest that SAC could protect against the neuronal cell death induced by the activation of caspase-12 in primary cultures and OHC. It is also suggested that multiple mechanisms may be involved in neuronal death induced by AI3 and AI3 in combination with IBO.

• Archives of Pharmacal Research
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• 제18권6호
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• pp.391-395
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• 1995

Several lines of evidence indicate that physiological activity of N-methyl-D-aspartate (NMDA) receptor was blocked by physiological concentration of $Mg^{2+}$ (1.2 mM). However, the activity of NMDA receptor may not be blocked totally with this concentration of $Mg^{2+}$ under elevated membrane potential by kainate. Here, we described the effect of $Mg^{2+}$ on NMDA receptor and how much of NMDA receptor functions could be activated by kainate. Effects of NMDA receptor antagonist on kainate-induced elevation of intracellualr $Ca^{2+}$ levels $([Ca^{2+}]_i)$ and extracellular glutamate level were examined in cultured rat cerebellar granule neurons. kainate-induced elevation of $([Ca^{2+}]_i)$ was not affected by physiological concentration of $Mg^{2+}$. Kainate-induced NMDA-induced elevation was blocked by the same concentration of $MG^{2+}$Kainate-induced elevation of [$([Ca^{2+}]_i)$ was decreased by 32% in the presence of NMDA antagonists, MK-801 and CPP (3-[2-carboxypiperazine-4-yl]propyl-1-phosphonic acid), in $Mg^{2+}$ free buffer. Kainate receptor-activated gluamate release was also decreased (30%) by MK-801 or CPP. These resuts show that certain extent of elevations of intracellular $Ca^{2+}$ and extracellular glutamate by kainate is due to coativation of NMDA receptors.

• Archives of Pharmacal Research
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• 제25권3호
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• pp.349-356
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• 2002

The present study was performed to examine the effect of fangchinoline, a bis- benzylisoquinoline alkaloid, which exhibits the characteristics of a $Ca^{2+}$ channel blocker, on cyanide-induced neurotoxicity using cultured rat cerebellar granule neurons. NaCN produced a concentration-dependent reduction of cell viability, which was blocked by MK-801, an N-methyl-D-aspartate (NMDA) receptor antagonist, verapamil, L-type$Ca^{2+}$channel blocker, and L-NAME, a nitric oxide synthase inhibitor. Pretreatment with fangchinoline over a concentration range of 0.1 to 10 $\mu$M significantly decreased the NaCN-induced neuronal cell death, glutamate release into medium, and elevation of $[Ca^{2+}]_i$ and oxidants generation. These results suggest that fangchinoline may mitigate the harmful effects of cyanide-induced neuronal cell death by interfering with $[Ca^{2+}]_i$influx, due to its function as a $Ca^{2+}$ channel blocker, and then by inhibiting glutamate release and oxidants generation.

• Archives of Pharmacal Research
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• 제20권1호
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• pp.7-12
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• 1997

Glutamate uptake inhibitor, L-trans-pyrrolidine-2, 4-dicarboxylate (PDC, $20{\mu}M$) elevated basal and N-methyl-D-aspartate (NMDA, $100{\mu}M$)-induced extracellular glutamate accumulation, while it did not augment kainate $100{\mu}M$-induced glutamate accumulation in cultured cerebellar granule neurons. However, pretreatment with PDC for 1 h significantly reduced NMDA-induced glutamate accumulation, but did not affect kainate-induced response. Pretreatment with glutamate $(5{\mu}M)$ for 1 h also reduced NMDA-induced glutamate accumulation, but did not kainate-induced response. Upon a brief application (3-10 min), PDC did neither induce elevation of intracellular calcium concentration $([Ca^{2+}]_i)$ nor modulate NMDA-indLiced $[Ca^{2+}]_1$ elevation. Pretreatment with PDC for 1 h reduced NMDA-induced $[Ca^{2+}]_1$ elevation, but it did not reduce kainate-induced $[Ca^{2+}]_1$ elevation. These results suggest that glutamate concentration in synaptic clefts of neurana cells is increased by prolonged exposure (1 h) of the cells to PDC, and the accumulated glutamate subsequently induces selective desensitization of NMDA receptor.

• 생명과학회지
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• 제15권4호
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• pp.607-612
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• 2005

열충격단백질 70 (HSP70)은 복수유전자족으로서 통상적으로 표현되는 Hsc70와 스트레스에 의하여 유도되는 Hsp70가 있다. 포유동물의 신경계통에서는 상당한 량의 HSP70가 정상조건에서도 표현되는 것으로 알려져 있다. 본 연구에서는 흰쥐의 소뇌 세포의 연접에서 Hsp70의 표현에 대한 연구를 하였다. 면역조직화학적으로 소뇌절편을 염색하여 관찰한 결과 Hsp70와 Hsc70 모두 표현되었는데, 소뇌 조롱박세포에서 가장 강하게 표현되었으며, 다음으로 소뇌 과립세포에서 강하게 표현되었다. 또한 깊은소뇌핵의 신경세포들도 강하게 염색되었다. 배양한 P1 소뇌신경 세포를 Hsp70 항체로 염색한 결과 Hsp70는 조롱박세포와 과립 세포에서 모두 표현되었으며, 세포체와 가지돌기를 따라 점박이를 형성하였다. 이들 점 박이들은 PSD95 점박이와 같이 위치하였다. 그리고 PSD 분획을 이용한 면역염색에서도 PSD70이 검출되었다. 본 연구결과는 Hsp70이 정상조건에서도 소뇌신경세포의 연접에 존재함을 의미한다.

• Animal cells and systems
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• 제1권2호
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• pp.381-388
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• 1997

Glutamate is a putative excitatory neurotransmitter in the central nervous system. The present study utilizing monoclonal antibodies against fixative-modified glutamate analyzed the distribution of glutamate-immunoreactive neuronal elements in the dog basilar pons. The glutamatergic neurons were present throughout the rostrocaudal extent of the basilar pons, predominantly to the medial and ventral subdivisions. Labelled cells were relatively sparse in the midline region of the medial nucleus and most lateral area of the lateral nucleus. The majority of glutamate-immunoreactive neuronal somata in the basilar pons was multipolar-shaped, and the size was in the range of 15-25 ${\mu}$m in diameter. Glutamate-immunoreactive axons and terminals were also observed at specific regions of the basilar pons. These observations provide evidence that this excitatory neural element functions in a multisynaptic pathway involving glutamatergic afferents to the basilar pons, pontocerebellar projection neurons, and the granule cells of the cerebellar cortex.

• Biomolecules & Therapeutics
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• 제16권4호
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• pp.328-335
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• 2008

This study was undertaken to investigate whether honokiol could enhance the pentobarbitalinduced sleeping behaviors through $\gamma$-aminobutyric acid (GABA) receptor $Cl^-$ channel activation. Thirty minutes after the oral administration of honokiol, mice were received sodium pentobarbital (42 mg/kg, i.p.). The time elapsed from pentobarbital injection to the loss of the righting reflex was taken as sleeping latency. The time elapsed between the loss and voluntary recovery of the righting reflex was considered as the total sleeping time. Western blot technique and $Cl^-$ sensitive fluorescence probe were used to detect the expression of $GABA_A$ receptor subunits and $Cl^-$ influx in the primary cultured cerebellar granule cells. Honokiol (0.1 and 0.2 mg/kg) prolonged the sleeping time induced by pentobarbital (42 mg/kg) in a dosage-dependent manner. Honokiol (20 and 50 ${\mu}M$) increased $Cl^-$ influx in primary cultured cerebellar granule cells, and selectively increased the $GABA_A$ receptor $\alpha$-subunit expression, but had no effect on the abundance of $\beta$ or $\gamma$-subunits. Chronic treatment with 20 ${\mu}M$ honokiol in primary cultured cerebellar neurons did not affect the abundance of GAD65/67. The results suggested that honokiol could potentiate pentobarbital-induced sleeping through $GABA_A$ receptor $Cl^-$ channel activation.

• Archives of Pharmacal Research
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• 제22권1호
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• pp.48-54
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• 1999

These studies were designed to examine the differential effect of nitric oxide (NO) and cGMP on glutamate neurotransmission. In primary cultures of rat cerebellar granule cells, the glutamate receptor agonist N-methyl-D-aspartate (NMDA) stimulates the elevation of intracellular calcium concentration ($[Ca^{2+}]_i$), the release of glutamate, the synthesis of NO and an increase of cGMP. Although NO has been shown to stimulate guanylyl cyclase, it is unclear yet whether NO alters the NMDA-induced glutamate release and ${[Ca^{2+}]}_i$ elevation. We showed that the NO synthase inhibitor, NG-monomethyl-L-arginine (NMMA), partially prevented the NMDA-induced release of glutamate and elevation of ${[Ca^{2+}]}_i$ and completely blocked the elevation of cGMP. These effects of NO on glutamate release and [Ca2+]i elevation were unlikely to be secondary to cGMP as the cGMP analogue, dibutyryl cGMP (dBcGMP), did not suppress the effects of NMDA. Rather, dBcGMP slightly augmented the NMDA-induced elevation of ${[Ca^{2+}]}_i$ with no change in the basal level of glutamate or ${[Ca^{2+}]}_i$. The extracellular NO scavenger hydroxocobalamine prevented the NMDA-induced release of glutamate providing indirect evidence that the effect of NO may act on the NMDA receptor. These results suggest that low concentration of NO has a role in maintaining the NMDA receptor activation in a cGMP-independent manner.

• 한국약용작물학회지
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• 제11권4호
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• pp.298-305
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• 2003

Polygalae Radix (PR) from Polygala tenuifolia. (Polygalaceae) is traditionally used in China and Korea, since this herb has a sedative, antiinflammatory, and antibacterial agent. To extend pharmacological actions of PR in the CNS on the basis of its CNS inhibitory effect, the present study examined whether PR has the neuroprotective action against kainic acid (KA) -induced cell death in primarily cultured rat cerebellar granule neurons. PR, over a concentration range of 0.05 to $5{\mu}g/ml$ inhibited KA $(500\;{\mu}M)$-induced neuronal cell death, which was measured by a trypan blue exclusion test and a 3-[4,5-dimethylthiazol-2-y1]-2,5-diphenyl-tetrazolium bromide (MTT) assay. PR $(0.5{\mu}g/ml)$ inhibited glutamate release into medium induced by KA $(500\;{\mu}M)$, which was measured by HPLC. Pretreatment of PR $(0.5{\mu}g/ml)$ inhibited KA $(500\;{\mu}M)$-induced elevation of cytosolic calcium concentration $([Ca^{2+}]_c)$ which was measured by a fluorescent dye, Fura 2-AM, and generation of reactive oxygen species (ROS). These results suggest that PR prevents KA-induced neuronal cell damage in vitro.