The Effect of Estrogen on Passive Avoidence Memory in an Experimental Model of Alzheimer's disease in Male Rats

Estrogen is one of the gonadal hormones that has multiple beneficial actions in central nervous system and involves in learning and memory. Alzheimer's disease (AD) is a progressive neurodegenerative disorder that impairs patient memory. The human nucleus basalis of Meynert (nBM) is severely affected in Alzheimer's disease. So in this study the effect of peripheral (intramuscular) injection of estradiol banzoate on passive avoidance memory was investigated in adult male wistar rats. nBM bilateral electrical lesion rats were divided in to control, lesion, sham (lesion+ 0.2ml sesame oil) and estradiol treatment (lesion+ 0.2, 0.4, 0.8, 1.2 mg/kg). After injection estradiol or sesame oil (vehicle) each rat was trained by shuttle box one week. In this study two factors, latency in entering dark chamber and time spending in the dark chamber was considered. Statistical analysis showed that nBM bilateral lesion decrease the passive avoidance memory (P<0.01). Injection 0.2mg/kg estradiol does not improve memory. While injection 0.4 and 0.8mg/kg estradiol have improved memory (p<0.05, p<0.01). But injection 1.2 mg/kg estradiol does not have distinctive effect on passive avoidance memory. Estradiol benzoate affects passive avoidance memory in a dose dependent manner. It seems that estrogen improve memory through an interaction with cholinergic system via genomic and non-genomic mechanisms.