Hypoxia-ischaemia model in the 7-day-old rat: possibilities and shortcomings.

The Levene model in 7-day-old rats is the most often used model of hypoxia-ischaemia (HI) in immature animals. The rat central nervous system is immature at birth and corresponds neurodevelopmentally to the term human infant during the second postnatal week. The Levene model of HI differs from clinical asphyxia with respect to the unilateral distribution of brain injury and lack of multi-organ dysfunction. Furthermore, it does not allow cardiovascular monitoring or repeated blood sampling. On the other hand, the progressive nature of HI bears many similarities to birth asphyxia with regard to blood flow changes and cellular metabolic derangements. The model is well characterized, easy to carry out and the low cost allows inclusion of a sufficient number of animals for dose-response evaluation of neuroprotective agents. In addition, it provides the unique opportunity of long-term evaluation of neuropathological and functional outcome.