Involvement of hippocampal agmatine in β1-42 amyloid induced memory impairment, neuroinflammation and BDNF signaling disruption in mice

Abstract

Alzheimer's disease (AD) is a chronic and progressive neurodegenerative disorder characterized by abnormal accumulation of extracellular β-amyloid (Aβ) plaques and neuronal damage. The present study investigated the effect of chronic intra-hippocampal agmatine administration on β-Amyloid (Aβ) induced memory impairment in mice. Aβ1-42 peptide injected mice demonstrated impairment of cognitive abilities evaluated as reference memory error and working memory error in radial arm maze (RAM) and decreased exploration time for novel object as well as recognition index in novel object recognition (NOR) test along with elevation in Aβ1-42 peptide, β-Site APP cleaving enzyme 1 (BACE 1), microtubule-associated protein tau (MAPt), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α) and reduction in neprilysin and brain derived neurotrophic factor (BDNF) immunocontent within hippocampus and prefrontal cortex. Importantly, this was associated with a reduction in the agmatine levels following Aβ1-42 peptide administration. Chronic administration of agmatine from day 8–27, prevented the memory impairment in mice and normalized the neurochemical alteration within prefrontal cortex and hippocampus induced by Aβ1-42 peptide administration. However, it did not modulate the amyloid precursor protein and BACE expression. This study suggests that agmatine improves learning and memory impairment possibly through the down regulation of neuroinflammatory pathways in AD.