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Likewise, the plasma concentrations of catecholamines and angiotensin, assessed in dogs, proved to be elevated during the acute phase of VO, but less is known about the chronic hormonal fluctuations in permanent VO.Finally, even though acute changes in the plasma concentration of corticosterone have not been recorded, our experiments demonstrated that VO persisting for months caused a significant increase in the circulating corticosterone level in a stressful situation. Even though these changes have been primarily associated with reperfusion injury, the results from the VO experiment infer that cerebral hypoperfusion itself may generate a systemic inflammatory response.Systolic blood pressure was measured repeatedly on freely moving, awake rats with the tail cuff method.However, as the experimental evidence presented here compellingly demonstrates, cerebrovascular injury can evoke a complex set of systemic reactions.Two species frequently employed for carotid occlusion studies are the rat and the gerbil.These two models create distinct ischemic conditions in the brain.Because of the lack of communicating arteries between the carotid and vertebral systems, carotid occlusion in the gerbil leads to severe forebrain ischemia.Besides the clearcut differences between species, a number of studies have also drawn attention to variations between strains.Even a particular rat strain from different suppliers may be the source of differences in ischemic tolerance.All these data suggest that, depending on the cerebrovascular condition to be reproduced experimentally, the most suitable strain must be chosen for the purpose.Furthermore, data analysis and comparison with results published by others must take any strain differences into account.The method of anesthesia applied must be considered because various anesthetics may exert different effects on the autonomic responses and cerebral metabolic rate in the VO model.In this respect, the effects of different anesthetics on physiological measures such as the mean arterial pressure and heart rate have been evaluated in VO rats.Under sodium th iopen tal, sod ium pen toba rbital,or a lpha ch lo ra lose anesthesia, VO elicited a systemic arterial pressor response comparable to that in conscious animals, while ketamine hydrochloride plus acepromazine was not as reliable.The stability of the baseline values for heart rate and arterial pressure indicated that sodium thiopental and sodium pentobarbital were the most suitable anesthetics for the measurement of systemic responses to VO are thought to furnish neuroprotection in ischemia by reducing the cerebral metabolic rate, some research groups have set out to characterize and compare the neuroprotective capacities of these agents.When VO was combined with hypotension, which also resulted in isoelectric EEG, measurement of the histological damage in the hippocampus pointed to isoflurane as the most neuroprotective anesthetic. However, when the EEG activity was maintained in the same model, no significant difference in neuroprotection could be established between isoflurane, ketamine, and fentanyl. Furthermore, isoflurane has been shown to attenuate ischemiainduced glutamate release in the hippocampus. A few attempts have recently been made to refine the VO model in order to avoid the acute phase directly after the occlusion.These studies focus on exploring technical solutions so as to be able to examine the neural consequences of gradually developing chronic cerebral hypoperfusion, or of atherosclerosis in the carotid bifurcation, as occurs in human aging and dementia.

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