Diabetes-Induced Prefrontal Nissl Substance Deficit and the Effects of Neem-Bitter Leaf Extract Treatment

Abstract

Cognitive dysfunction is reportedly associated with poorly-managed diabetes mellitus. In this study, we report the effect of oral treatment with combined leaf extract (CLE) of neem and bitter leaf on the prefrontal cortex of diabetic Wistar rats. Adult male Wistar rats were randomized to one of the following groups: control, diabetic (STZ-induced), STZ + CLE, STZ + metformin and CLE only. At euthanasia, paraffin sections of the prefrontal cortex were stained with cresyl fast violet; while malondialdehyde (MDA) and glutathione peroxidase (GPx) were assayed in prefrontal homogenates. Oral CLE produced normoglycemia in the treated hyperglycaemic rats. Besides, Nissl-stained prefrontal sections showed no morphologic deficits in all the groups except the untreated diabetic rats. In the latter, there was weak Nissl staining, while prefrontal MDA was significantly high at euthanasia, compared with the control and CLE-treated rats (P<0.05). This study showed that untreated diabetes mellitus is associated with prefrontal Nissl body deficit and oxidative stress in Wistar rats. The absence of these deficits in CLE-treated rats suggests a neuroprotective effect of the extract in streptozotocin-induced diabetic rats. This may improve the cognitive function of the prefrontal cortex in diabetes mellitus.