Effect of wogonin on spatial memory and its possible mechanisms in chronic cerebral ischemia in rats

Objective To investigate the effect of wogonin on ethology and its possible mechanisms in chronic cerebral ischemia in rats. Methods Ratswere randomly divided into a sham operation group, awogonin intervention group, and a phosphate buffered solution(PBS) control group. A rat model of chronic cerebral ischemia was induced by the two-vessel occlusion method. Six weeks after modeling, the rats in the wogonin intervention group and the PBS control group were intragastric administrated with wogonin (50μmol/L, 10 ml/kg, once a day)and PBS with equal volume for 14 days. Morris water maze test was used to evaluate the spatial learning and memory function. Laser confocal three-dimensional vascular imaging was used to detect the vascular proliferation of ischemic brain tissue. 5-Bromo-2-deoxyuridine (BrdU) immunochemical staining was used to detect the cell proliferation in ischemic brain tissue. Transmission electron microscope was used to observe the morphological changes of neural cells in cerebral ischemic region. Results The Morris water maze (n=8) showed that the trains of escape latency from the second to the fifth day in the wogonin intervention group were 43.45±8.64s, 37.12±1.31s, 34.75±5.36s, and 24.36±5.43s, respectively. They were significantly shorter than 51.69±5.32s, 43.65±9.21s, 50.19±10.31 s, and 53.65±7.15 s in the PBS control group (all P< 0.05). The first quadrant swimming time of the wogonin intervention group was significantly longer than that of the PBS control group (26.16±3.29 s vs. 14.38±2.16 s;P< 0.01). Laser confocal three-dimensional vascular imaging (n=4) showed that the capillary inner diameter in cerebral ischemia region of the wogonin intervention group was reduced significantly compared to the PBS control group (3.02±0.21μm vs. 3.35±0.18μm; P< 0.05), vascular density was increased significantly(205.80±12.70/0.002 mm3vs. 158.42±10.92/0.002 mm3;P< 0.01), and total microvascular area was increased significantly (83389±4026μm2/0.002 mm3 vs. 73349±3986μm2/0.002 mm3; P< 0.01). Immunohistochemical staining (n=6) showed that the number of BrdU positive cells in the ischemic brain tissue of the wogonin intervention group was increased significantly compared to the PBS control group (24.62±3.25/HPF vs. 9.87±2.89/HPF;P< 0.01). The observation of transmission electron microscope showed that the inflammatory edema in the intercellular spaces of the wogonin intervention group was significantly reduced compare to the PBS control group. Conclusions Wogonin can significantly improve the spatial learning and memory ability of chronic cerebral ischemia in rats, and its possible mechanisms may include the promotion of proliferation and angiogenesis in ischemic region and angiogenesis, and reduce inflammatory response. Key words: Brain Ischemia; Cognition Disorders; Maze Learning; Memory; Flavanones; Wogonin; Neovascularization, Physiologic; Neuroprotective Agents; Rats