The effect of pre-training infusions of estrogen receptor ligands in the CA1 region of hippocampus on passive avoidance task

Background: Neurohormones like testosterone and estrogen play important roles in learning and memory. Estrogen receptors, densely expressed in the CA1 region of rat hippocampus, mediate the effects of estrogen on learning and memory. Estrogen receptors belong to a family of transcription factors, the nuclear receptor super family, and have two subtypes, estrogen receptor α and estrogen receptor β. Objectives: Study the effect of pre-training infusions of estrogen receptor ligands in the CA1 region of hippocampus on passive avoidance task Materials and Methods: The current research has been conducted to assess the effects of estradiol valerat, estrogen receptor β selective agonist, diarylpropionitrile, nonsteroidal selective estrogen receptor β modulator, and Cyclofenil on passive avoidance task on adult male rats. Male adult rats were bilaterally cannulated into the CA1 area of hippocampus, and then administered vehicle dimethyl sulfoxide or estradiol valerat (15 μg/0.5μl/side), diarylprop-ionitrile (0.2, 0.5, 1 μg/0.5μl/side), Cyclofenil (5, 7.5,10 μg/0.5μl/side), 30 min before training. Results: Results showed that pre-training intra CA1 injections of EV (15 μg/0.5μl/side), diarylpropionitrile (0.5, 1 μg/0.5μl/side), and Cyclofenil (10 μg/0.5μl/side), significantly decreased step-through latencies and increased time spent in the dark chamber in inhibitory avoidance learning. Conclusions: Our data suggest that estrogen receptor β plays has an important role in learning and memory acquisition in the inhibitory avoidance task. A R T I C L E I N F O Article history: Received: 7 May 2010 Revised: 10 Jul 2010 Accepted: 4 Sep 2010