Susceptibility of hippocampus and cerebral cortex to oxidative damage in streptozotocin treated mice: prevention by extracts of Withania somnifera and Aloe vera.

Diabetes mellitus is reported to impair the memory function in experimental animals. Since the mammalian hippocampus and cerebral cortex play a pivotal role in a diverse set of cognitive functions, such as novelty detection and memory, we examined the vulnerability of cortex and hippocampus regions of the brain to oxidative damage in streptozotocin (STZ) diabetic mice. We next examined the attenuating effect of extracts of Withania somnifera and Aloe vera on prevention of hippocampal and cortical cell degenerations. Doses of both plant extracts given to experimental animals were based on the evaluation of their total antioxidant activity and also their potency to reduce Fe(3+). We assayed lipid peroxidation (LPO) and protein carbonyl (PC) in both regions of the brain and observed the changes in memory and motor behavioral functions in diabetic and control mice. The results showed a significant (P < 0.05) increase in LPO and PC in hippocampus and cortical regions of STZ diabetic mice. We also found a significant impairment in both motor and memory behavioral functions in diabetic mice. However, when diabetic mice were supplemented with the extracts of Withania somnifera and Aloe vera, the oxidative damage in both brain regions was reduced as marked by a significant (p < 0.05) declines in both LPO and PC. The combination of extracts of Withania somnifera and Aloe vera was more effective in reducing oxidative damage in brain regions than the supplementation of single plant extract. The combination also lowered the blood glucose level in comparison to STZ diabetic mice. Memory impairment and motor dysfunction were also improved by the plant extracts supplementation. We conclude that impairments in the hippocampus and cortex in STZ diabetic mice are associated with an increased free radical mediated oxidative damage and that the supplementation of plant extracts showed preventive effects in attenuating oxidative damage in both brain regions possibly via antioxidative mechanisms.