Exact location of sensorimotor cortex injury after photochemical modulation; evidence of stroke based on stereological and morphometric studies in mice.

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The integrity of the structural cerebral cortex is disrupted after stroke either at the macroscopic or microscopic levels. Therefore, many attempts have been gathered to circumvent stroke-associated problems in the brain tissue. The current study was aimed to design an animal model of photochemical stroke using rose bengal (RB) plus laser irradiation (L) after 10, 15, and 20min (´) and evaluate its effect on the cerebral tissue using unbiased stereological quantitative methods and morphometric histological analysis. Photochemical stroke was induced by intraperitoneal injection of RB dye and further activation through the exposure of the right sensorimotor cortex with the green laser radiation (100mW; 532nm). Mice were randomly allocated into 4 groups (each in 15) as follows: control (10μg/gbw RB), RB + 10'L, RB + 15'L, and RB + 20'L. Target irradiation site was adjusted to 2mm lateral to the bregma. Vernier caliper morphometric evaluation, cresyl violet staining, and unbiased stereological assays including Cavalier's principle and point counting techniques were used to monitor the pathological changes and lesion volume on days 1, 3, and 7 after the ischemia induction. Our data showed that the mean diameter of the lesion site and lesion infarct volume in the group RB + 20'L) was significantly increased relative to the other groups (P< 0.05). Notably, the lesion volume and diameter in the group RB + 15'L was larger compared with the group RB + 10'L and control mice (P< 0.05). Data showed an increased acute inflammatory response such as hyperemia and edema 3days after ischemic induction while the intensity of acute changes and lesion volume were reduced and replaced with necrotic and chronic pathological changes including astrogliosis on day 7. It is concluded that the laser irradiation of RB-injected mice at a distinct time period could induce the magnificent degenerative effects on the cerebral cortex which is similar to the stroke condition.