Enriched environment restores passive avoidance memory impairment in a rat model of neuroinflammation

Neuroinflammation is a primary pathophysiological condition that is associated with cognitive impairment and neurodegenerative diseases. The present study was designed to evaluate the effects of enriched environment (EE) on passive avoidance (PA) memory impairment caused by lipopolysaccharide (LPS) induced neuroinflammation.

Twenty-eight male Wistar rats were assigned into the following groups: 1, control; 2, control+ EE; 3, LPS and 4, LPS+ EE. LPS injection (1mg/kg/i.p.) was done on days 1, 3, 5 and 7 of experiment. Two different housing conditions were used in this experiment, including a standard environment house and an enriched environment house. The passive avoidance task was used to examine animals learning and memory performance. The hippocampal level of interleukin-6 (IL-6) and brain-derived neurotrophic factor (BDNF) was also measured using sandwich-ELISA method.

Obtained data indicated that LPS significantly impaired passive avoidance memory, decreased the step-through latency and increased the time spent in the dark compartment of the LPS treated group compared to the control group. On the other hand, EE housing could significantly ameliorate memory impairment. Hippocampal IL-6 level was increased and BDNF was decreased in the LPS group, whereas EE could decrease and increase IL-6 and BDNF levels in the LPS+EE group, respectively.

EE should probably be considered as an alternative strategy in neuroinflammatory diseases to minimize the memory impairment.