Exposure to intermittent hypoxia impairs learning and memory ability in rats

Abstract

To study the effects of chronic intermittent hypoxia (CIH) on learning and memory ability in Sprague–Dawley rats, we established a rat model of CIH. A total of 24 male Sprague–Dawley rats were included and were assigned to three experimental groups (n = 8/group): the unhandled control (UC) group (normal feeding for 4 weeks), the CIH group (CIH for 4 weeks), and the removal of hypoxia (RH) group (normal feeding for 4 weeks after CIH for 4 weeks). All the results were analyzed using one-way ANOVA and comparison between groups was performed using S–N–K method. Performance on the Morris water maze test (a learning and memory test) was significantly worse for CIH rats than for UC rats and RH rats (P < 0.05), but was significantly better for RH rats than for UC rats (P < 0.05). Synaptophysin expression in the CA3 region of the hippocampus was reduced in the CIH group and the RH group compared with the UC group (P < 0.05), but was significantly greater in the RH group than in the CIH group (P < 0.05). Synaptophysin is a calcium-binding protein located in the membranes of presynaptic vesicles. Changes of synaptophysin expression may indirectly reflect the structural changes in the hippocampal CA3 region. In rats, CIH can cause declines in learning ability and memory and reduce the expression of synaptophysin in the CA3 region of the hippocampus; these effects could be partially rescued by the removal of hypoxic factors. The observed decline in learning and memory ability in rats may relate to a decrease in synapse quantity and structural changes in the CA3 region of the hippocampus.