Microsphere embolism-induced changes in noradrenaline uptake of the cerebral cortex in rats

Heartsick: psychiatric and inflammatory implications of cerebromicrovascular disease

BACKGROUND

Cerebromicrovascular disease (CMVD) strikes 87% of the population older than 65 years and is linked to an increased risk of ischemic stroke, depression, cognitive impairment, and Alzheimer's disease. Despite the wealth of knowledge on the consequences to the body stemming from poor vascular health, little focus has been placed on the consequences to the brain.

DESIGN

In this review, we present the preclinical and clinical evidence that supports the role of CMVD in behavioral dysfunction, argues for a clinical need for better recognition of the vascular depression phenotype, and calls for a more integrative translational approach to CMVD.

RESULTS AND CONCLUSIONS

Although the concept of cerebrovascular-induced behavioral change has existed for over 100 years, the difficulty of diagnosis, the slow progression of CMVD, and the lack of causative data have led to an underestimation of the patient population and poor treatment strategies. Preclinical studies have focused on the use of microsphere embolic models and vascular inflammation models to assess the mechanisms of, and treatment options for, CMVD. Though preclinical models provide support for correlative data collected in the clinic, translational reciprocity has not been established. The lack of clinical appreciation for the role of cerebrovascular health in brain function may result in missed diagnoses and inadequate treatment of underlying cardiovascular disease. Enhanced recognition of symptoms and disease presentation will allow for earlier prevention, detection, and identification of novel targets for drug development and other intervention strategies.

[The model of stroke induced by microsphere embolism in rats]

Cerebral infarction is induced by injecting 700-900 microspheres with a diameter of 50 microm into the right internal carotid artery of the rat. Approximately 82% of the rats with typical symptoms of stroke survived at fifteen hours after the injection of microspheres. Microsphere-induced cerebral embolism elicits the widespread formation of small emboli in the ipsilateral hemisphere and subsequent neuronal loss and/or the development of multiple infarct areas in the brain, particularly in the cortex, striatum, and hippocampus. Thus, this model is considered to mimic focal ischemia-induced human stroke or multi-infarct dementia. We have found that this model showed sustained decreases in cerebral blood flow and cerebral high-energy phosphates; accumulation of tissue lactate, glucose, and glycogen; changes in the activity of several enzymes in the tricarboxylic acid cycle; loss of mitochondrial phosphorylation activity; and decreases in neurotransmitters, acetylcholine, monoamines, and amino acids in the ipsilateral hemisphere. Accordingly, microsphere embolism is capable of inducing severe and sustained cerebral ischemia resulting in disturbances of the energy and neurotransmitter metabolism in the brain. Such ischemic damage leads to learning and memory dysfunction. This model provides useful information about the pathogenesis, prophylaxis, and therapeutics of cerebral ischemic diseases.