Hypoxia potentiates the memory deficit in Swedish mutant APP transgenic mice. A Morris water maze protocol with 1 day of visible platform tests and 4 days of hidden platform tests, plus a probe trial on day 6. Animal movement was tracked and recorded by an HVS 2020 Plus image analyzer (HVS Image, Hampton, UK). Ten mice per group were used for hypoxia and normoxia treatment. (A) During the first day of visible platform tests, mice were trained in five contiguous trials. The hypoxic and normoxic APP23 mice exhibited a similar latency to escape onto the visible platform. P > 0.05 by Student's t test. (B) Hypoxic and normoxic APP23 mice swam a similar distance before escaping onto the visible platform in the visible platform test. P > 0.05 by Student's t test. (C) In hidden platform tests, mice were trained with six trials per day for 4 days. Hypoxic APP23 mice showed a longer latency to escape onto the hidden platform. P < 0.005 by two-way ANOVA. (D) Hypoxic APP23 mice swam farther before escaping onto the hidden platform. P < 0.001 by two-way ANOVA. (E) In the probe trial on day 6, hypoxic APP23 mice crossed the target platform significantly fewer times than controls. ∗, P < 0.05 by Student's t test.