Simultaneous effect of food restriction and dopamine D2 receptor inhibition on spatial memory of male rats

Food restriction may have beneficial or detrimental effects on the brain functions such as learning and memory. Also, dopamine receptors are involved in learning and information retrieval. This study was performed to determine the simultaneous effect of food restriction and dopamine D2 receptor inhibition on spatial memory of rats.

In this experimental study, 60 male Wistar rats were allocated into 6 groups including controls, 25%, 50% and 75%, food restriction, sulpiride (D2 receptor antagonist, 4 mg/kg/day, ip), 75% food restriction and sulpiride and treated for 21 days. To evaluate the memory, an eight-point radial arm maze was used. Then, the catalase and malondialdehyde level of the hippocampus were measured.

Twenty-five percent food restriction caused to 11.8 percent decrease in spending time to find the food compared to control group (P<0.05). The 75% food restriction and or sulpiride injection significantly increased that time by 24.4% and 18.3%, respectively (P<0.05). The group with 75% food restriction were received sulpiride showed the most increase in the time of food finding compared to all groups (P<0.05). Catalase activity was only significantly reduced in the 75% restricted groups to 17.6% and 22.2%, respectively (P<0.05). Malondialdehyde production was significantly increased in the 75% food restricted groups to 50.2% and 59.3, respectively and sulpiride-received group to 31.2% compared to the control group (P<0.05).

Simultaneous applying of food restriction and inhibition of dopamine D2 receptors resulted in increased hippocampal prooxidant levels and exacerbated memory impairment.