The Role of Estrogen Receptors on Spatial Learning and Memory in CA1 Region of Adult Male Rat Hippocampus

The hippocampal system plays an important role in memory function. Neurohormones like androgens and estrogens that syntheses in hippocampus have an important role in learning and memory. Many biological effects of estrogens in the brain via estrogenic receptors (ERs) are investigated. The current research has conducted to assess the effect of estrogenic receptors on spatial discrimination in rats by using Morris water maze (MWM) task. Adult male rats were bilaterally cannulated into CA1 region of hippocampus and divided in to 9 groups. Different groups received dimethyl sulfoxide (DMSO) 0.5 µl as control groups and different doses of tamoxifen (TAX) as antagonist of ER (0.0625, 0.125 and 0.25µg/0.5µl), propyl pyrazol thiol (PPT) as agonist of ERα (5,10 and 20µg/0.5µl), TAX 0.25µg/0.5µl + PPT 20µg/0.5µl all days 30-35 min before training. Our results have shown TAX (0.25µg/0.5µl), PPT (20µg/0.5µl), TAX (0.25µg/0.5µl) + PPT (20µg/0.5µl) groups significantly increase the escape latency and traveled distance to find invisible platform. Our results indicate that TAX and PPT and also TAX (0.25µg/0.5µl) + PPT (20µg/0.5µl) impaired acquisition of spatial learning and memory. As a consequence, it seems that estrogen modulates memory function via a novel estrogenic mechanism.