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Experimental basis of multi-infarct dementia: memory impairments in rodent models of ischemia
1Division of Cerebral Circulation Research, National Cardiovascular Center, Osaka, Japan.
Abstract:
Memory is an intellectual function that is initially and consistently impaired in patients with vascular dementia. Experimental approaches to vascular dementia have so far been confined to investigations of memory impairments in rodent ischemic models. Unilateral middle cerebral artery (MCA) occlusion, multiple small embolization or transient four-vessel occlusion in rats produced acute single or multiple infarctions. In such rats, significant memory impairments occurred during the subacute or chronic phases, but were partially reversible. Permanent stenosis of both common carotid arteries in gerbils caused no ischemic changes at 1 day after stenosis but induced multiple infarctions after 1 week of stenosis, probably due either to chronic recurrent ischemia resulting from transient repetitive obstruction of the carotid arteries or to chronic low perfusion. The memory impairments in this model were persistent. Permanent bilateral common carotid artery occlusion in rats produced multiple infarctions plus white matter changes after 1 week of occlusion. Marked memory impairment was also observed in this model. The results of the above studies suggest that memory impairments due to ischemic causes may be partially reversible provided that the infarctions occur only once and are followed by flow recovery. Memory impairments, however, appear to persist if the brain is exposed to chronic recurrent ischemia or chronic moderately low perfusion. A repetitive or persistent low-flow state appears to be an important factor in determining the irreversibility of cognitive impairments.
Insights
Vascular dementia memory impairments may improve after a single ischemic event if blood flow recovers. However, persistent or recurrent ischemia leads to irreversible cognitive deficits in rodent models.
Area of Science:
- Neuroscience
- Vascular Dementia Research
- Ischemic Stroke Models
Background:
- Memory impairment is a hallmark of vascular dementia.
- Rodent models are crucial for studying experimental approaches to vascular dementia.
- Understanding the mechanisms of memory loss in ischemia is vital.
Purpose of the Study:
- To investigate the reversibility of memory impairments in rodent models of vascular dementia.
- To explore the impact of different ischemic patterns on cognitive function.
- To identify factors contributing to persistent versus reversible memory deficits.
Main Methods:
- Utilized rodent models including middle cerebral artery (MCA) occlusion, embolization, and carotid artery stenosis.
- Induced acute, recurrent, and chronic low-flow ischemic conditions.
- Assessed memory function during subacute and chronic phases post-ischemia.
Main Results:
- Single ischemic events followed by flow recovery showed partially reversible memory impairments.
- Chronic recurrent ischemia or sustained low perfusion resulted in persistent memory deficits.
- Permanent bilateral carotid occlusion led to multiple infarctions and white matter changes with marked memory impairment.
Conclusions:
- Memory impairments in vascular dementia may be reversible after single ischemic insults with reperfusion.
- Chronic or repetitive ischemia and persistent low perfusion are linked to irreversible cognitive decline.
- The nature and duration of ischemic insult significantly influence memory recovery in vascular dementia models.