Protective Effects of Enriched Environment Against Transient Cerebral Ischemia-Induced Impairment of Passive Avoidance Memory and Long-Term Potentiation in Rats

Background and Aim : schemic stroke is one of the main causes of long lasting neurological defects, emotional, and memory dysfunction. One mechanism possibly contributing to learning and memo ry deficits is impairment in the hippocampal Long-Term Potentiation (LTP). LTP is facilitated by exposure to Enriched Environment (EE) or exercise. Among others, EE has been shown to impact the development of the nervous system. How ever, it is still unclear whether adolescent exposure to EE can be used as an efficient preventive strategy against LTP function impairment associated with global hypo perfusion. Thus, the present study aimed to evaluate the protective effects of EE in adolescent period against the impairment of passive avoidance memory and LTP in duced by transient cerebral ischemia in adult male rats.Methods : Male Wistar (n=30) rats and housed in Standard Environment. The EE group was located in a large polycar bonate containing a running wheel, a raised platform, a group of plastic tunnels, steel chains, dissimilar size plastic balls and dolls changed every 5-6 days. The SE group was housed in normal Plexiglas cages. Rats were dispersed into 3 experimental groups: 1. The SHAM/ SE group: those animals which raised in SE and had the bilateral common carotid arteries exposed but received no additional manipulation; 2. The STR/SE group: those animals which raised in SE and had the bilateral com mon carotid arteries exposed and induced transient 2VO occlusion for 30 min; and 3. The STR/EE group: those animals which raised in EE and had transient 2 Vessel Occlusion (2VO) for 30 min. For analysis of the passive avoidance data, 1-way ANOVA with the Tukey post hoc test and mann Whitney U-test was used.Results : post hoc analysis revealed that transient cerebral ischemia significantly decreased STL in the STR/SE group than the SHAM/SE group. In addition, increased STL in the STR/ EE group than the STR/SE group and, increased TDC in the STR/SE group compared with SHAM/SE group. also, increased TDC in the STR/EE group compared to STR/SE group. there were significant differences in stimulus-response curves in the DG measured as PS amplitude between the STR/SE group and the SHAM/SE group in high intensities. There was no significant difference in stimulus-response curves in the DG measured as EPSP slopes. In the STR/SE group, tetanus HFS stimulation resulted a increase in the PS amplitude in the SHAM/SE group and increase was also induced after HFS in the STR/EE. a significant decrease in the PS amplitude of the SHAM/SE group than the STR/SE group. Tetanus HFS had no significant effect on EPSP slope recorded from the DG area of hippocampus in the STR/ ST group compared to sham control rats, but there were significant differences in the STR/EE rats compared to STR/SE rats in 60, 75, and 90 min.Conclusion : Our results suggest that early housing and growing in EE exhibits therapeutic potential to normalize cognitive and LTP abnormalities induced by 2VO ischemic model in rats.

Keywords:

Enriched Environment , Long-Term Potentiation , Ischemia-Induced