ABSTRACT
<p><b>AIM</b>To study the relationship between changes of learning, memory and orphanin FQ (OFQ) in hippocampus of rats in acute hypobaric hypoxia at two different altitude levels of 4 500 m(moderate) and 7 500 m(serious).</p><p><b>METHODS</b>Hypobaric chamber, Morris water maze training method and RT-PCR technique were used in the experiment.</p><p><b>RESULTS</b>(1) Compared with the control, the OFQ mRNA expression of hippocampus increased significantly after exposure to acute serious hypobaric hypoxia (8 h/d for 6 d in succession), but obviously decreased after Morris water maze training (6 times/d for 6 d in succession, the latency of place navigation was shortened). (2) After exposure to acute hypobaric hypoxia, the latency of place navigation was markedly elongated, but the OFQ mRNA of hippocampus was significantly higher than that of learning and memory group.</p><p><b>CONCLUSION</b>The hippocampal OFQ was involved in the mechanism of decrease in spatial learning and memory induced by acute hypobaric hypoxia.</p>