EN
Mild hypobaric hypoxia (MHH) which is known to induce tolerance to brain hypoxia/ischemia, appeared to prevent development of anxiety and depressive-like behavior in rats submitted to the unavoidable adversive stress. The latter effect of unclear mechanism so far wasnít confi rmed in other animal models. Since enhanced brain expression of the neuropeptide Y (NPY) mimics effects of anxiolytic and antidepressant drugs, and we noticed that MHH increases the number of NPY-positive neurons in the gerbil hippocampus, we propose possible involvement of NPY in the positive behavioral effects of MHH. The aim of present study was to reproduce behavioral effects of MHH in balb/c57 mice using the tail suspension test and the elevated plus maze, and to evaluate immunohistochemically in these animals the number of NPY-positive neurons in the hippocampus. We confi rmed that intermittent MHH (360 Torr, 2 h for 3 consecutive days) in mice induces anxiolytic and weak antidepressant-like effects. The elevated plus maze trials performed 48 h after MHH revealed a signifi cant increase in frequency of the open arm entries, reduced duration of the closed arm occupancy, and 7-fold increased time spent on the open arms in comparison to sham animals. In the tail suspension a signifi cant decrease of the duration of immobility was observed 24 h, but not 48 h after MHH, when we detected a modest but signifi cant increase in the number of NPY-positive neurons in the hippocampus. Thus, although our preliminary data confi rm anxiolytic and antidepressant-like effects of MHH in mice, further studies are needed to characterize better these effects and to learn its mechanism, particularly to verify the role of NPY. Supported by the Scientifi c Network Fund no 26/E-40/SN0023/2007