Neuroprotective effects of forsythiaside on learning and memory deficits in senescence-accelerated mouse prone (SAMP8) mice.

Forsythiaside (3,4-dihydroxy-β-phenethyl-O-α-L-rhamnopyranosyl-(1→6)-4-O-caffeo yl-β-d-glucopyranoside, C29H36O15), which is isolated from air-dried fruits of Forsythia suspensa, has been shown to possess anti-oxidant, anti-bacterial and anti-inflammatory activities. The aim of this study is to investigate the neuroprotective effects of forsythiaside on learning and memory deficits in the senescence-accelerated mouse prone 8 (SAMP8, a model of age-dependent neurodegenerative disorders such as Alzheimer's disease). Forsythiaside (60, 120 and 240mg/kg) was orally administered to aged (8months old) SAMP8 mice for 45days followed by evaluating cognitive impairment (Morris water maze and step-through passive avoidance), inflammation (interleukin-1β (IL-1β) and interleukin-6 (IL-6) levels), oxidative stress (glutathione peroxidase (GSH-Px) and total superoxide dismutase (T-SOD) activities; malondialdehyde (MDA) and nitric oxide (NO) contents) and neurotransmitter such as norepinephrine (NE), dopamine (DA), 5-hydroxytryptamine (5-HT), glutamate (GLU) gamma-aminobutyric acid (GABA) and acetyl choline (ACh). In Morris water maze, forsythiaside had significantly reduced the latency time, the crossing numbers and time spent in target quadrant compared to aged SAMP8 mice. In passive avoidance test, a significant decline in number of errors while increase in latency was observed when compared with aged SAMP8 mice. Furthermore, a significant decrease in IL-1β, NO, MDA and NE levels, and an increase in T-SOD and GSH-Px activities and GLU and Ach levels were evident in the brain homogenates of forsythiaside-treated mice compared to aged SAMP8 mice. These findings demonstrated that forsythiaside may be a useful treatment against amnesia.