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Kohei Sawada

Publications and source records attributed to Kohei Sawada.

7 recordsLinked to original sources
PubMed2006

Protective effect of donepezil in primary-cultured rat cortical neurons exposed to N-methyl-d-aspartate (NMDA) toxicity.

Donepezil has a neuroprotective effect against oxygen-glucose deprivation injury and glutamate toxicity in cultured cortical neurons. In this study, we further characterized the neuroprotective properties of donepezil in rat cortical cell cultures using glutamate receptor-specific agonists (N-methyl-d-aspartate (NMDA), alpha-amino-3-hydroxy-5-methylisoxazolepropionate (AMPA) and kainate). Pretreatment with donepezil (1 microM) for 12 h significantly decreased the lactate dehydrogenase (LDH) release in response to NMDA (100 microM) by 43.8%, and reduced the LDH release in response to kainate (100 microM) and AMPA (100 microM) by 11.9% and 7.5% (without statistical significance), respectively. Donepezil appeared to inhibit LDH release in a concentration-dependent manner at 0.1-10 microM. Cortical neurons exposed to NMDA retained a normal morphological appearance in the presence of 10 microM donepezil. In binding assay for glutamate receptors, donepezil at 100 microM only slightly inhibited binding to the glycine and polyamine sites on NMDA receptor complex. On the other hand, 12 h pretreatment with donepezil at 10 and 100 microM significantly decreased the NMDA-induced increase of intracellular calcium concentration ([Ca2+]i). In conclusion, our results show that donepezil has protective activity against NMDA toxicity in cortical neurons, and this neuroprotection seems to be partially mediated by inhibition of the increase of [Ca2+]i.

Animals↗
PubMed2006

[KCNQ channels].

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Animals↗
PubMed2005

Comparison of donepezil and memantine for protective effect against amyloid-beta(1-42) toxicity in rat septal neurons.

Donepezil, a potent acetylcholinesterase (AChE) inhibitor and memantine, an N-methyl-d-aspartate (NMDA) receptor antagonist, have been used for the treatment of Alzheimer's disease (AD), and both of them have been shown to have neuroprotective action against glutamate excitotoxicity. However, it is not known whether donepezil and memantine similarly exert neuroprotective effects against amyloid-beta peptide(1-42) [Abeta(1-42)] toxicity in cholinergic neurons. Therefore, in the present study we compared the neuroprotective effects of donepezil and memantine against Abeta(1-42) toxicity in rat cultured septal cholinergic neurons, because deficit in cholinergic neurotransmission is a major feature in AD, and medial septal cholinergic neurons are known to degenerate in AD patients. Septal neuronal cells were cultured for 7 days and then 5 micromol/L of Abeta(1-42) was added to the medium for 48 h. Measurement of the efflux of lactate dehydrogenase (LDH) indicated that septal neuronal cells were highly susceptible to Abeta toxicity and relatively resistant to NMDA toxicity. Donepezil concentration-dependently reduced the LDH efflux induced by Abeta(1-42), and the effect was significant at 1 micromol/L and above. NMDA receptor antagonists, memantine and MK-801, did not show a significant neuroprotective effect against Abeta(1-42) toxicity. It is concluded that the neuroprotective effect of donepezil against Abeta(1-42) toxicity is not mediated by interference with the NMDA-mediated excitotoxic process, and that donepezil may be more effective than memantine against cholinergic neuronal damage induced by Abeta(1-42) exposure.

Acetylcholinesterase↗
PubMed2005

Protective effect of donepezil against Abeta(1-40) neurotoxicity in rat septal neurons.

Donepezil, a potent acetylcholinesterase (AChE) inhibitor used for the treatment of Alzheimer's disease (AD), is thought to have a neuroprotective effect in AD patients. Because a deficit in cholinergic neurotransmission is a major feature in AD, and amyloid-beta (Abeta) accumulation has been proposed as a possible causative phenomenon, we were interested to examine the effect of donepezil on Abeta(1-40) induced neurotoxicity in primary cultures of rat septal neurons. Using immunohistochemical staining, almost all the neurons were found to be positive for vesicular acetylcholine transporter (VAChT) in these septal cultures. Septal neuronal cells were cultured for 7 days and then 15 micromol/L of Abeta(1-40) was added to the cell medium for 48 h. The cultured septal neurons were highly susceptible to Abeta toxicity, as shown by morphological examination and lactate dehydrogenase (LDH) assay. Donepezil concentration-dependently reduced the LDH efflux induced by Abeta(1-40), and the effect was significant at 100 nmol/L and above. Donepezil decreased both the negative peak at around 215 nm in the circular dichroism (CD) spectrum and the fluorescence intensity of thioflavin T in the presence of Abeta(1-40). These results suggest that donepezil exerts a neuroprotective effect by reducing the amount of the toxic form of Abeta fibrils in septal neuron cultures. These findings support the idea that the clinical efficacy of donepezil in AD is due to not only activation of cholinergic transmission, but also attenuation of neuronal damage.

Acetylcholine↗
PubMed2003

Olprinone for the treatment, but not prevention, of fatigue-induced changes in guinea-pig diaphragmatic contractility.

UNLABELLED: Olprinone, a phosphodiesterase III inhibitor, improves the contractility in fatigued diaphragm in vivo, but no data are available for the treatment and prevention of fatigue-induced changes in vitro. We therefore examined the efficacy of Olprinone for the treatment and prevention of fatigue-induced changes in guinea-pig diaphragmatic contractility. The guinea-pig diaphragm strips were randomly allocated according to dose of Olprinone (0, 10(-6), 10(-5), and 10(-4) M) (n = 7 each) and were stimulated directly in an organ bath. Diaphragmatic contractility was measured by assessing twitch tension and force at 20-Hz and 100-Hz stimulation. Diaphragmatic fatigue was induced by generating rhythmic, repetitive contractions produced by 20-Hz stimulation for 5 min. In the first experiment, after the fatigue-producing period, Olprinone was administered to the organ bath for 5 min. In the second experiment, Olprinone was pretreated for 5 min, and then diaphragmatic fatigue was produced. In Experiment 1, after a fatigue-producing period, tetanic force to each stimulus decreased from baseline values (P < 0.05). Olprinone 10(-5)-10(-4) M caused an increase in force at both stimuli from fatigued values (P < 0.05). In Experiment 2, no change in tetanic force was observed by pretreatment with Olprinone (0-10(-4) M). After producing fatigue, tetanic force to each stimulus decreased from baseline values (P < 0.05). These results suggest that Olprinone 10(-5)-10(-4) M improves the fatigue-induced changes in guinea-pig diaphragmatic contractility and that pretreatment with Olprinone does not prevent diaphragmatic fatigability. IMPLICATIONS: Olprinone is effective for the treatment, but not prevention, of fatigue-induced changes in guinea-pig diaphragmatic contractility.

Animals↗
PubMed2002

Ca(2+) channel alpha(1B) subunit (Ca(V) 2.2) knockout mouse reveals a predominant role of N-type channels in the sympathetic regulation of the circulatory system.

N-type voltage-dependent Ca(2+) channels (VDCCs), predominantly localized in the nervous system, have been proposed to play vital roles in a variety of neuronal functions such as neurotransmitter release at sympathetic nerve terminals. To directly approach the elucidation of the physiological significance of N-type VDCCs in the autonomic nervous system, alpha(1B) subunit (Ca(V) 2.2)-deficient mice were generated, in which peripheral neurons showed a complete and selective elimination of N-type channel currents sensitive to omega-conotoxin GVIA (the peptide toxin from the fish-hunting cone snail Conus geographus), without a significant effect on the activity of other VDCC types. In isolated left atria prepared from N-type-deficient mice, the positive inotropic response mediated by the sympathetic nervous system was dramatically decreased, whereas the negative inotropic response mediated by parasympathetic neurons was nearly intact compared with those of normal mice. The baroreflex response to bilateral carotid occlusion was markedly reduced in the mutant mice. Interestingly, the mutant mice showed sustained elevation of heart rate and blood pressure. These results provide direct in vivo evidence for an essential role of N-type VDCCs in maintaining the normal function of the sympathetic nervous system in circulatory regulation, demonstrating a potential of N-type VDCC-deficient mice as a useful model for studying disorders attributable to sympathetic nerve dysfunction.

Animals↗