Hypoxic Preconditioning. Search for a Predictor of Its Efficiency

A single moderate hypobaric hypoxia (HBH) prolongs the resistance (T, the time before apnoea) to
severe hypobaric hypoxia (SHBH). This hypoxic preconditioning effect has good therapeutic potential.
In our study on the intact rats and those pre-tested under SHBH with low, intermediate and high
resistance to it, we found that the hypoxic preconditioning eliminated the differences in resistance to
severe hypoxia between groups of rats with different innate resistance to it and with different prior
hypoxic experiences. It was logical to conclude that the hypoxic preconditioning is realized by its own
mechanisms. To investigate these mechanisms, methods for predicting an efficiency of
preconditioning action were needed, but such methods were not available. In the process of
searching, we discovered in the intact rats a strong association between the efficiency of HBH and
prepulse inhibition (PPI) in the acoustic startle reaction model, which we called the PPI-T test. This
model is widely used in neurobiology and psychiatry; however, PPI has not previously been used as
an indicator of hypoxic preconditioning. Therefore, we have demonstrated its validity. The PPI-T test
can be used to predict the performance of the preconditioning action on the intact animals and to
study its mechanisms.