Cerebral blood flow in the monkey. Electroencephalographic effects of temporary occlusion of the carotid and vertebral arteries at varying levels of systemic arterial pressure

Selection of preclinical models to evaluate intranasal brain cooling for acute ischemic stroke

Stroke accounts for a large proportion of global mortality and morbidity. Selective hypothermia, via intranasal cooling devices, is a promising intervention in acute ischemic stroke. However, prior to large clinical trials, preclinical studies in large animal models of ischemic stroke are needed to assess the efficacy, safety, and feasibility of intranasal cooling for selective hypothermia as a neuroprotective strategy. Here, we review the available scientific literature for evidence supporting selective hypothermia and make recommendations of a preclinical, large, animal-based, ischemic stroke model that has the greatest potential for evaluating intranasal cooling for selective hypothermia and neuroprotection. We conclude that among large animal models of focal ischemic stroke including pigs, sheep, dogs, and nonhuman primates (NHPs), cynomolgus macaques have nasal anatomy, nasal vasculature, neuroanatomy, and cerebrovasculature that are most similar to those of humans. Moreover, middle cerebral artery stroke in cynomolgus macaques produces functional and behavioral deficits that are quantifiable to a greater degree of precision and detail than those that can be revealed through available assessments for other large animals. These NHPs are also amenable to extensive neuroimaging studies as a means of monitoring stroke evolution and evaluating infarct size. Hence, we suggest that cynomolgus macaques are best suited to assess the safety and efficacy of intranasal selective hypothermia through an evaluation of hyperacute diffusion-weighted imaging and subsequent investigation of chronic functional recovery, prior to randomized clinical trials in humans.

Mnemonic and neuropathological effects of occluding the posterior cerebral artery in Macaca mulatta

To investigate experimentally the mnemonic and neuropathological effects of blockage of the posterior cerebral arteries (PCA), a cerebrovascular accident that can lead to global anterograde amnesia in humans, we permanently occluded these arteries bilaterally in six monkeys and then evaluated their performance on a visual recognition task, after which we assessed the extent of their ischemic infarcts. The latter showed substantial individual variation, ranging from almost no damage in one case to massive unilateral injury of both the ventromedial o occipitotemporal cortex and hippocampal formation in another. In the four remaining cases, however, the infarcts fell within a narrow range, being confined almost entirely to the hippocampal formation and parahippocampal gyrus, and then only to restricted portions of these structures, unilaterally in one case, and bilaterally in the three others. Performance on the recognition task was related to the presence and bilaterality of the hippocampal injury. Thus, the case without any hippocampal damage performed at a rate equal to that of normal controls; the case with unilateral hippocampal damage was mildly impaired; and the three cases with bilateral infarctions, involving between 20 and 55% of the hippocampal formation, showed substantial impairment, with scores averaging 20% below those of normal controls. The only subfields of the hippocampus damaged in common in these cases were CA1 and CA2. Paradoxically, the memory loss found in these three animals with only partial bilateral hippocampal damage was significantly greater than that found in animals with total bilateral ablation of the hippocampal formation, whose scores averaged only 10% below those of normal controls. Possible explanations for this extremely puzzling outcome are proposed.

Hemodynamic and metabolic concomitants of brain swelling and cerebral edema due to experimental cerebral infarction

✓ Severe cerebral ischemia was produced in 25 baboons by clamping the carotid and vertebral arteries bilaterally for 10 minutes. Cerebral hemodynamics and metabolism were monitored throughout. Cerebral anoxia was less severe in animals in which a marked pressor response occurred due to ischemia of the vasomotor center, and a reversible type of brain swelling was usual. In those with more severe ischemic anoxia, progressive cerebral edema was a pathological entity. Evidence is presented that cerebral edema was caused by loss of autoregulation of cerebral blood flow (CBF) concomitant with hyperemia and an increase of water and chloride content of brain tissue. Cerebral edema began when CBF was reduced during occlusion and progressed for several hours after termination of occlusion. Evidence is adduced that uncoupling of oxidative phosphorylation may be an important concomitant of cerebral edema.