Protective Effect of Buckwheat Polyphenols Against Long-Lasting Impairment of Spatial Memory Associated With Hippocampal Neuronal Damage in Rats Subjected to Repeated Cerebral Ischemia

Abstract

Abstract. In the present experiment, we studied the action of buckwheat polyphenol (BWP, from Fagopyrum esculentum MOENCH) in a repeated cerebral ischemia model, which induced a strong and long-lasting impairment of spatial memory in 8-arm radial maze with hippocampal CA1 cell death in rats. BWP (600 mg / kg, continuous 21-day p.o.) significantly ameliorated not only the impairment of spatial memory in the 8-arm radial maze, but also necrosis and TUNELpositive cells in the hippocampal CA1 area subjected to repeated cerebral ischemia (10 min´2 times occlusion, 1-h interval) in rats. In order to investigate the mechanism of BWP protective action, we measured the release of glutamate and NO x -(NO 2 -+ NO 3 -) production induced by repeated cerebral ischemia in the rat dorsal hippocampus using microdialysis. A 14-day BWP treatment significantly inhibited the excess release of glutamate after the second occlusion. In addition, the BWP remarkably suppressed a delayed increase in NO x -(NO 2 -+ NO 3 -) induced by repeated cerebral ischemia in the dorsal hippocampus as determined in vivo by microdialysis. However, the 14-day treatment did not affect hippocampal blood flow in either intact rats or rats subjected to repeated ischemia measured by lasser Doppler flowmeter. These results suggested that BWP might ameliorate spatial memory impairment by inhibiting glutamate release and the delayed generation of NO x -in rats subjected to repeated cerebral ischemia.

Neuroprotective Effects of Quercetin and Rutin on Spatial Memory Impairment in an 8-Arm Radial Maze Task and Neuronal Death Induced by Repeated Cerebral Ischemia in Rats

“…We have previously reported that 14-day pre-ischemic treatment with buckwheat polyphenol, but not 7-day post-ischemic treatment, attenuates spatial memory impairment and neuronal death induced by repeated cerebral ischemia (15). Therefore, we used the pretreatment schedule.…”

“…Behavioral testing using the 8-arm radial maze task (Neuroscience Co., Tokyo) was conducted as previously reported (15). The maze consisted of a central platform, 24 cm in diameter, with 8 arms extending radially.…”

“…Cerebral ischemia was carried out in animals that had acquired spatial memory according to our previous report (15). Briefly, rats were anesthetized with sodium pentobarbital (50 mg / kg, i.p.)…”

“…In this model, changes in the mRNA level of the AMPA receptor subunit GluR2 and bcl family expression in the hippocampus following reperfusion are thought to be related to the appearance of TUNEL-positive cells in the CA1 region (13,14). We have studied the effects of buckwheat polyphenol, which includes rutin, quercetin, catechin, and oligonols of catechin, in this repeated cerebral ischemia model (15). In this experiment, we used this model to study the differential effects of rutin, quercetin, catechin, and EGCG on spatial memory impairment and neuronal death in the hippocampal CA1 region.…”

Measurement of optic nerve blood flow during dissection of parasellar tumors

“…ONBF was measured using a laser Doppler flowmeter (TBF-LN1, Unique Medical, Tokyo, Japan) [25,30]. The contact probe (10 mm in major axis; LP-UCS, Unique Medical, Fig.…”