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Abstract
Studies examining the roles of estrogens and progestins on spatial cognition have
been highly contradictory. To determine if the hormonal environment of pregnancy affects
spatial cognition, pregnant (n = 7) and virgin (n = 7) Hooded Long-Evans rats were
tested in a Morris water maze throughout the 3 weeks of pregnancy and the second week
postpartum. Latency to platform, path length, swim velocity, and time in quadrant
were compared over trial-days. To compare water maze performance with changes in hormone
levels, serum concentrations of estradiol and progesterone were measured on the first,
third, and fifth days of testing during the third week of pregnancy. Subjects learned
to find the platform as indicated by decreased time and distance to platform over
each trial-week and increased time spent in the quadrant where the platform had been
located the previous week. However, there were no differences between treatment groups
on time or distance to platform over trial-days. Swim velocity did not differ between
or within groups over the 4 weeks of testing. Although primigravid and virgin females
were similar in their abilities to learn the novel location of a submerged platform
and return to it over time, pregnant animals demonstrated less perseveration to previously
learned information and were quicker to locate the platform when it moved to a new
location. Thus, reproductive status did not affect reference memory but enhanced working
memory in the Morris water maze.