Abstract
The positive roles of antioxidants on brain development and learning and memory have been suggested. Nigella sativa (NS) has been suggested to have antioxidant and neuroprotective effects. This study was done to investigate the effects of feeding by the hydro-alcoholic extract of NS during neonatal and juvenile growth on learning and memory of rats. The pregnant rats were kept in separate cages. After delivery, they were randomly divided into four Groups including: (1) control; (2) NS 100 mg/kg (NS 100); (3) NS 200 mg/kg (NS 200); and (4) NS 400 mg/kg (NS 400). Rats in the control group (Group 1) received normal drinking water, whereas Groups 2, 3, and 4 received the same drinking water supplemented with the hydro-alcoholic extract of NS (100 mg/kg, 200 mg/kg, and 400 mg/kg, respectively) from the 1st day after birth through the first 8 weeks of life. After 8 weeks, 10 male offspring from each group were randomly selected and tested in the Morris water maze (MWM) and passive avoidance (PA) test. Finally, the brains were removed and total thiol groups and malondialdehyde (MDA) concentrations were determined. In the MWM, treatment by 400 mg/kg extract reduced both the time latency and the distance traveled to reach the platform compared to the control group (p < 0.05-p < 0.01). Both 200 mg/kg and 400 mg/kg of the extract increased the time spent in the target quadrant (p < 0.05-p < 0.01). In the PA test, the treatment of the animals by 200 mg/kg and 400 mg/kg of NS extract significantly increased the time latency for entering the dark compartment (p < 0.05-p < 0.001). Pretreatment of the animals with 400 mg/kg of NS extract decreased the MDA concentration in hippocampal tissues whereas it increased the thiol content compared to the control group (p < 0.001). These results allow us to propose that feeding of the rats by the hydro-alcoholic extract of NS during neonatal and juvenile growth has positive effects on learning and memory. The effects might be due to the antioxidant effects.