Protective Effect of Low-Intensity Pulsed Ultrasound on Memory Impairment and Brain Damage in a Rat Model of Vascular Dementia

Purpose To investigate the neuroprotective effects of low-intensity pulsed (LIP) ultrasound on memory impairment and central nervous system injury in a rat model of vascular dementia. Materials and Methods All animal experiments were approved by the animal care and use committee and adhered to experimental animal care guidelines. A 1.0-MHz focused ultrasound transducer was used to stimulate the brain noninvasively with 50-msec bursts at a 5% duty cycle, repetition frequency of 1 Hz, and spatial peak temporal average intensity of 528 mW/cm². LIP ultrasound treatment was performed daily with triple sonications in each hemisphere. The duration of each sonicaton was 5 minutes, with a 5-minute interval between each sonication. Permanent bilateral common carotid artery occlusion (BCCAO) was used as a model of vascular dementia. After 2 weeks of LIP ultrasound, neuroprotective effects of LIP ultrasound were evaluated with behavioral analysis, including the passive avoidance task and elevated plus maze. Myelin content was detected with carbon 11 (¹¹C) Pittsburgh compound B (PIB). Brain sections were stained with hematoxylin-eosin and Luxol fast blue. Two-way analysis of variance and Student t test were used for statistical analyses, with a significance level of .05. Results Protein expressions of brain-derived neurotrophic factor (BDNF) in the BCCAO rats treated with LIP ultrasound were significantly higher than those in BCCAO rats (1.1 ± 0.0 vs 0.8 ± 0.1, P < .05). BCCAO rats exhibited neuronal damage and demyelination. Compared with the BCCAO group, ¹¹C PIB accumulation in the BCCAO rats treated with LIP ultrasound was significantly (P < .05) increased by 67.4% and 203.0% in the hippocampus and corpus callosum, respectively. Hematoxylin-eosin staining showed that neuronal injury in the hippocampal cornu ammonis 1 region was alleviated with LIP ultrasound. Luxol fast blue staining of the corpus callosum was significantly greater in the BCCAO rats treated with LIP ultrasound than in the untreated BCCAO rats (mean, 94.5% ± 2.3 [standard error] vs 86.6% ± 1.0; P < .05). Moreover, LIP ultrasound stimulation significantly improved learning and memory abilities and morphology in rats with vascular dementia compared with rats with untreated vascular dementia (P < .05). Conclusion These results suggest LIP ultrasound stimulation protects against brain injury in the hippocampus and corpus callosum in rats with vascular dementia. The beneficial effect of LIP ultrasound may be partly induced by upregulation of protein expression of BDNF. ^© RSNA, 2016.