Abstract
Thymus vulgaris L. is an aromatic herb used for medicinal purposes such as antimicrobial, spasmolytic, antioxidant, anti-inflammatory, antinociceptive, antitumor, and may have beneficial effects in the treatment of Alzheimer’s disease. The present study aimed to investigate whether Thymus vulgaris L. essential oil enhances cognitive function via the action on cholinergic neurons using scopolamine (Sco)-induced zebrafish (Danio rerio) model of memory impairments. Thymus vulgaris L. essential oil (TEO, 25, 150, and 300 µL/L) was administered by immersion to zebrafish once daily for 13 days, whereas memory impairment was induced by Sco (100 μM), a muscarinic receptor antagonist, delivered 30 min before behavioral tests. Spatial memory was assessed using the Y-maze test and novel object recognition test (NOR). Anxiety and depression were measured in the novel tank diving test (NTT). Gas Chromatograph-Mass Spectrometry (GC-MS) analysis was used to study the phytochemical composition of TEO. Acetylcholinesterase (AChE) activity and oxidative stress response in the brain of zebrafish were determined. TEO ameliorated Sco-induced increasing of AChE activity, amnesia, anxiety, and reduced the brain antioxidant capacity. These results suggest that TEO may have preventive and/or therapeutic potentials in the management of memory deficits and brain oxidative stress in zebrafish with amnesia.
Highlights
Alzheimer’s disease (AD) is a progressive neurodegenerative condition with significant variability in clinical characteristics and biomarkers and numerous genetic and environmental factors implicated in its etiology and development [1,2]
AD poses issues of progressive episodic memory and executive performance across cognitive continuums ranging from cognitively unimpaired (CU), moderate cognitive impairment (MCI), to AD [3]
Non-cognitive symptoms associated with AD and related dementias include insanity, mood disorders, behavioral changes, agitation, anger, slowness, wandering, altered sexual activity, modified sleep habits, and eating disorders [7]
Summary
Alzheimer’s disease (AD) is a progressive neurodegenerative condition with significant variability in clinical characteristics and biomarkers and numerous genetic and environmental factors implicated in its etiology and development [1,2]. Oxidative stress is known to be a very significant factor in ageing and age-related disorders and a large amount of research has shown that oxidative stress is an important pathogenic factor in AD [8]. Protein oxidation markers, such as protein carbonyls, have been shown to be increased in AD brains in areas with proven histopathological AD characteristics [9]. Protein carbonyls and 3-nitrotyrosine (3-NT) levels have been increased in the frontal cortex of individuals with MCI, mild AD, and AD, with no distinction between disease stages, a finding that supports the concept of oxidative stress as an early event in AD [10]
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