COMPOUND MECHANISM HYPOTHESIS ON +Gz-INDUCED BRAIN INJURY AND DYSFUNCTION OF LEARNING AND MEMORY

摘要

We systematically studied the effect of high-sustained +Gz on the brain and its mechanism in past ten years by animal centrifuge experiments. On the basis of the facts we observed and the more recent advances in acceleration physiology, we put forward a compound mechanism hypothesis to offer a possible explanation for +Gz-induced brain injury and dysfunction of learning and memory. It states that, ischemia during high G exposure might be the main factor accounting for +Gz-induced brain injury and dysfunction of learning and memory, including transient depression of brain energy metabolism, disturbance of ion homeostasis, increased blood-brain barrier permeability, increased brain nitric oxide synthase expression, and the protective effect of heat shock protein 70. In addition, the large rapid change of intracranial pressure and increased stress during +Gz exposure, and the hemorrheologic change after +Gz exposure might be one of the important factors accounting for +Gz-induced brain injury and dysfunction of learning and memory. Modern high performance aircraft is capable of reaching accelerations as high as +9Gz sustained for 15-45s that may exceed the human physiological tolerance. It is well known that +Gz-induced loss of consciousness (G-LOC) that is the main threat for pilots is classically attributed to a decrease in cerebral blood flow that results from a drastic decrease in cerebral perfusion pressure. In addition, a causal relationship might exist between G-LOC and increased stress. Centrifuge training developed in many countries is considered as an appropriate method for preventing G-LOC. The benefits of centrifuge training are an increased G-tolerance resulting from improved skill in performing an anti-G straining maneuver and a better understanding of physiologic mechanisms of G-stress and G-tolerance. However, does repeated G-LOC cause the organic mental syndrome? Are the effects of these exposures additive? We know little about the potential pathophysiological effects of repeated high +Gz exposures on the brain.