Piperine has been shown to have
antioxidant activity and a cognitive-enhancing effect following long-term
oral administration. In a comparative study of
memantine, the current investigation threw light on the cognitive benefits of
piperine. Lipid peroxidation and the ferric reducing
antioxidant power (FRAP) of cerebrospinal fluid (CSF) and hippocampus in
streptozotocin (STZ)-induced experimental
dementia of the Alzheimer's type was measured. After reaching a criterion in a memory test, STZ-induced rats received
piperine [2.5, 5, and 10mg/kg, intraperitoneally (i.p.)], vehicle, and
memantine (10mg/kg, i.p.) for two weeks after the first STZ administration, or two weeks before and one week after, as a preventive approach. After the behavioral studies, samples were taken for biochemical and histological assays. An appropriate concentration of
piperine (2.5mg/kg), on a daily basis, effectively increased the number of correct (non-repeated) arm entries and repressed reentry to a previously visited arm, in terms of reference errors as well as
memantine (10mg/kg, i.p.), irrespective of the dose administered. The cognitive-enhancing effect induced by
piperine at a relevant dose was simultaneous with CSF and hippocampal
malonaldehyde decrement, and the redox balance was established to some extent by maintaining the FRAP levels of CSF near to those of the control. Similarly, the neuroprotective properties of
piperine are in accordance with histopathological outcomes, which have shown an increased number of live
cresyl violet (CV)-positive neurons in a dentate gyrus (DG) subregion. Therefore, the effects of
piperine on the redox balance of CSF and hippocampal neurons may certainly contribute to the cognitive-enhancing activity of the drug.