Severe 3-h hypobaric hypoxia was followed by impairment of Ca(2+)-mediated glutamatergic signal transduction in the posthypoxic period (no less than 72 h). This impairment manifested in changes in the calcium response to glutamate application in slices of rat brain cortex. Moderate hypoxic preconditioning prevented these disturbances developed over the first day after sever hypoxia.