Abstract

Twenty-eight, adult, male, 10 - 14 weeks old Wistar rats weighing 190 - 220 g were divided into four groups: unstressed control (U-Control), unstressed + Lycopene (U+Lyco), stressed control (S-Control) and stressed + Lycopene (S+Lyco), to investigate the effect of lycopene on stressed rats. Olive oil was administered by oral gavage to each rat in the groups, either singly or mixed with 10 mg/kg lycopene for two weeks. Only the S-Control and S+Lyco were subjected to novel environment of the open-field apparatus and step-down inhibitory avoidance task. The result indicates that in S+Lyco, lycopene decreased novelty-induced anxiety behavior as evidenced by an increased centre square frequency (P < 0.001) and duration (P < 0.001); ameliorated the effect of fear during the avoidance task as shown by increased learning acquisition (P < 0.01) and short-term memory retention (P > 0.05). Subjection to psychological stress significantly decreased superoxide dismutase (SOD) and catalase (CAT) activity in the brain of stressed groups compared to the unstressed groups. Lycopene supplementation further decreased brain malondialdehyde concentration (P < 0.05) in S+Lyco compared to S-Control. In conclusion, lycopene decreased oxidative stress biomarker in the brain, and this mechanism may be partly responsible for the enhancement of the behavioral and cognitive responses in Wistar ratssubjected to psychological stress.

Key words: Lycopene, behavior, cognition, psychological stress, brain stress biomarker.