Repeated Training Creates Spatial Memory in an Adult Male Rat Model of Testosterone-Induced Spatial Learning Impairment

Abstract

Background: Memories are primarily defined as the fragmentary or partial reconstruction of what were actually experienced at the time of acquisition. Spatial learning is assessed through repeated trials and reference memory is assessed by the measurement of latency in finding a concealed platform preference for the platform area when the platform is not present. Our daily experience, as well as learning experiments performed in animal studies, has enabled us to know that the formation of long-lasting memory needs repeated practice. Objectives: Our study aimed to investigate the effect of repeated training on spatial learning impairment, which was induced by the administration of testosterone in young adult rats. Methods: Cannula were bilaterally implanted into the Cornu Ammon (CA1) region of the hippocampus while testosterone (Testosterone Enantate, Aburaihan Pharmaceutical Company, Tehran) was daily microinjected for 3 minutes in each side. In this study, twenty-four male adult rats were divided into three groups as follows: the control group that received no treatment, the sham group that received DMSO as a drug solvent, and the treatment group that received testosterone at a dose of 80 μg/0.5 μL DMSO/each side injected into the CA1 before each session. Results: The results showed that the bilateral administration of testosterone into the CA1 region significantly increased the escape latency and the distance traveled by rats compared with the control and sham groups in the acquisition test. However, in the probe test (retrieval) there was no difference between the treatment group and other groups considering the escape latency and traveled distance. Conclusions: It seems that intra CA1 microinjection of testosterone causes the impairment in spatial learning. Repeated training enhances spatial learning in the Morris water maze (MWM) task, which leads to repeated long-term potentiation (LTP), spinogenesis, increased spine density, and spontaneous generation of new spines, resulting in the improvement of spatial memory in retrieval test.