ABSTRACT
<p><b>AIM</b>To explore the effect of chronic hypoxic hypercapnia on learning-memory and the possible mechanisms involved.</p><p><b>METHODS</b>Fifty-eight male SD rats were randomly divided into three groups: Normal control group (NC, n=18), 2-week (2HH, n=18), and 4-week hypoxic hypercapnia (4HH, n=20) group. The rats, spatial learning-memory tasks were assessed by the Morris water maze. The expression of NMDAR1mRNA was determined by hybridization in situ.</p><p><b>RESULTS</b>Compared with NC group, rats exposed to chronic hypoxic hypercapnia displayed significant impairment in their performance assessed by two measures: mean escape latencies (2HH: 38.59 +/- 8.35 s, 4HH: 60.59 +/- 17.28 s) and swim path distances(2HH: 9893.45 +/- 1958.16 mm, 4HH: 18077.57 +/- 6878.85 mm). The expression level of NMDAR1mRNA in the hippocampus and cortex were lower than those in the NC group, especially, the NMDAR1mRNA expression of hippocampus CA1 in 4HH decreased by 21.4% (P < 0.01).</p><p><b>CONCLUSION</b>Chronic hypoxic hypercapnia could impair the rat spatial learning-memory and the decrease in expression of NMDAR1mRNA might be involved in.</p>