Rehmannia glutinosa Ameliorates Scopolamine-Induced Learning and Memory Impairment in Rats

Abstract

Many studies have shown that the steamed root of Rehmannia glutinosa (SRG), which is widely used in the treatment of various neurodegenerative diseases in the context of Korean traditional medicine, is effective for improving cognitive and memory impairments. The purpose of this study was to examine whether SRG extracts improved memory defects caused by administering scopolamine (SCO) into the brains of rats. The effects of SRG on the acetylcholinergic system and proinflammatory cytokines in the hippocampus were also investigated. Male rats were administered daily doses of SRG (50, 100, and 200 mg/kg, i.p.) for 14 days, 1 h before scopolamine injection (2 mg/kg, i.p.). After inducing cognitive impairment via scopolamine administration, we conducted a passive avoidance test (PAT) and the Morris water maze (MWM) test as behavioral assessments. Changes in cholinergic system reactivity were also examined by measuring the immunoreactive neurons of choline acetyltransferase (ChAT) and the reactivity of acetylcholinesterase (AchE) in the hippocampus. Daily administration of SRG improved memory impairment according to the PAT, and reduced the escape latency for finding the platform in the MWM. The administration of SRG consistently significantly alleviated memory-associated decreases in cholinergic immunoreactivity and decreased interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) mRNA expression in the hippocampus. The results demonstrated that SRG had a significant neuroprotective effect against the neuronal impairment and memory dysfunction caused by scopolamine in rats. These results suggest that SRG may be useful for improving cognitive functioning by stimulating cholinergic enzyme activities and alleviating inflammatory responses.

<i>In Vivo</i> Screening of Traditional Medicinal Plants for Neuroprotective Activity against Aβ42 Cytotoxicity by Using <i>Drosophila</i> Models of Alzheimer’s Disease

“…9,[40][41][42] The antioxidant properties of P. multiflorum water extract suppressed cognitive deficits induced by Aβ accumulation in mice. 9) We also found that P. multiflorum ethanol extract exerts neuroprotective effect and has antioxidant properties in both Drosophila and human cell AD models; this suggested that both water and ethanol extracts of P. multiflorum contains beneficial components for neuronal health, and that the neuroprotective mechanism of P. multiflorum extract may be conserved from fly to human.…”

“…Neuroprotective effects of R. glutinosa have also been reported in several previous studies. 40,44,45) Moreover, catalpol, an iridoid glucoside isolated from the root of R. glutinosa, protected primary cultured cortical neurons from the Aβ42-induced damage, through a mitochondrial-dependent caspase pathway. 46) It is interesting to test whether catalpol also shows similar effect in our Drosophila models.…”

Protective effect ofPhellodendri Cortexagainst lipopolysaccharide-induced memory impairment in rats

“…These results showed that LPS infusion into the lateral ventricle of rat brains retarded escape latency in the MWM test, indicating deficits in spatial learning ability and reference memory. The scoring of the escape latency from water in the spatial probe tests in the MWM test is primarily considered to reflect long-term spatial memory ability (Lee et al 2011). In this study, administration of PCE shortened the escape latency without affecting swimming velocity and extended the time spent swimming in the place where the platform was previously located.…”

“…The test was performed according to the step-through method described previously (Lee et al 2011). The Gemini Avoidance System (SD Instruments., San Diego, CA, USA) was used for this test.…”

“…The MWM test was basically performed according to the MWM apparatus and the method described previously (Lee et al 2011). The animals received three trials per day.…”