Objective: 

Estrogen may affect learning and memory through modulating the function of the basal cholinergic system. Ovariectomy has been shown to alter not only cholinergic but also glutamatergic activity. Estrogen increases the density of synapse in hippocampus and plays a role spatial memory. However the findings on how estrogens affect hippocampal functions are controversial. We aimed to test locomotor activity and learning in chronic ovariectomized rats.

Methods: 

Experimental procedures were approved by Ethical Committee of Erciyes University. Thirty rats were randomly divided into ovariectomized and sham groups. After 6 weeks from ovariectomy open field and Y-maze test were performed to test locomotor activity and short-long term spatial learning, respectively.

Results: 

The total number of line crosses in periphery of open field arena was higher in sham group than ovariectomized group (p<0.03). Numbers for grooming (p<0.008) and freezing reaction (p<0.01) were statistically higher in ovariectomized group than sham group. In Y maze, sham group preferred to visit novel arm more frequently than familiar arm (p<0.05). The ovarectomized rats did not show any preference between the arms (p>0.05) in the short-term memory task. In the long-term memory task, the ovariectomized and sham groups' animals did not show any preference between the arms. The overectomized rats spent less time in the novel arm than the familiar arm in the short-term (p<0.05) and long-term tasks (p<0.05).

Conclusions: 

Chronic ovariectomized rats showed reduced locomotor activity and impaired spatial memory in short- and long-term tasks, but not in working memory tasks for retaining spatial information.