| Craniocerebral injury is a serious and complex trauma which include primary injury that result from outside force affecting directly on central nervous system and secondary injury which is caused by tissue reaction , physiopathologic change , hemorrhage and so on that base on primary injury. These secondary injuries are one of important reasons resulting in death or functional disorder of craniocerebral injury patients. However they can be prevented or controlled by reason of its occurrence following injury and its further development after receiving treating. Low mortality and good curative effect of cerebral injury patients dependent on effective treatment in secondary cerebral injury. Brain edema is one of the most common secondary injury. Discussing the mechanisms of brain edema and how to control effectively brain edema and brain swell are an important research field for neurosurgeon. Moreover, protection of blood-brain barrier (BBB) and alleviation of vasogenic brain edema after injuries are more attractive.BBB consist of several ultrastructure components. Capillary endotheliocyte and its tight junction are the main base of function and morphological structure of BBB. BBB disruption resulted from cerebral injury can cause permeability increasing of capillary endotheliocyte. Then, vasogenic brain edema come into being and brain hernia maybe form. Severe brain edema and high intracranial pressure can aggravate cerebral ischemia and anoxia on the contrary. Furthermore, harmful substance goes into cerebral tissue through destructive BBB. What we mentioned above cause serious injury of nerve function.Cerebral protection of mild hypothermia has been testified by many experimental and clinical studies. It was considered that mild hypothermia can reduce evidently mortality of craniocerebral injury patients or testing animals and promote nerve function to recover andameliorate pathomorphological change following craniocerebral injury. At present, it still has not enough understanding to cerebral protective mechanisms of mild hypothermia though many studies have been done. Therefore, many scholars are still attracted to the field and devote themselves to discussing cerebral protective mechanisms of mild hypothermia.Nowadays, studies of mild hypothermia on BBB following craniocerebral injury reported only in function and none in ultrastructure. Therefore, there still have some researching place in ultrastructure .In this article we observed ultrastructure changing of BBB after trauma by transmission electron microscope and observed the opening state of tight junction of endotheliocyte using the tracer of lanthanum. At the same time we measured water content of cerebral tissue around contusion by dry-wet weight means. We not only confirmed that there are BBB disruption, brain edema and their regularity following craniocerebral injury. Furthermore, we also discussed the effect of early mild hypothermia treatment after craniocerebral injury on morphology and function of BBB , effect on brain edema and their relativity in order to enrich cerebral protective mechanisms of mild hypothermia. It is beneficial to provide gists for further experimental studies and clinical application.Materials and MethodsBrain trauma of rat was induced in lobi parietalis by free falling object( improved Feeney's model). 126 rats were divided randomly into three groups:1. The normothermia non-traumatic group (n=14): Rats were only made an hole in cranial bone and given no hitting.2. The normothermia traumatic group (n=56): Rats were hit by 750g-cm on lobi parietalis to induce contusion model.3. The mild hypothermia-treated group (n=56) : Rats were cooled rapidly to 32.5 ± 0. 5 degree C for 3 hours after injury.Three groups were parted again into three sub-groups (ultrastructure group ., lanthanum tracing group . cerebral tissue water content group ) which are redivided into 3h,24h,48h and 72h four time phases(the normothermia non-traumatic group is not redivided). Every time phase have4 ra...
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