title: Repeated administration of fresh garlic increases memory retention in rats.
abstract: Garlic (Allium sativum) is regarded as both a food and a medicinal herb. Increasing attention has focused on the biological functions and health benefits of garlic as a potentially major dietary component. Chronic garlic administration has been shown to enhance memory function. Evidence also shows that garlic administration in rats affects brain serotonin (5-hydroxytryptamine [5-HT]) levels. 5-HT, a neurotransmitter involved in a number of physiological functions, is also known to enhance cognitive performance. The present study was designed to investigate the probable neurochemical mechanism responsible for the enhancement of memory following garlic administration. Sixteen adult locally bred male albino Wistar rats were divided into control (n = 8) and test (n = 8) groups. The test group was orally administered 250 mg/kg fresh garlic homogenate (FGH), while control animals received an equal amount of water daily for 21 days. Estimation of plasma free and total tryptophan (TRP) and whole brain TRP, 5-HT, and 5-hydroxyindole acetic acid (5-HIAA) was determined by high-performance liquid chromatography with electrochemical detection. For assessment of memory, a step-through passive avoidance paradigm (electric shock avoidance) was used. The results showed that the levels of plasma free TRP significantly increased (P < .01) and plasma total TRP significantly decreased (P < .01) in garlic-treated rats. Brain TRP, 5-HT, and 5-HIAA levels were also significantly increased following garlic administration. A significant improvement in memory function was exhibited by garlic-treated rats in the passive avoidance test. Increased brain 5-HT levels were associated with improved cognitive performance. The present results, therefore, demonstrate that the memory-enhancing effect of garlic may be associated with increased brain 5-HT metabolism in rats. The results further support the use of garlic as a food supplement for the enhancement of memory.
authors.affiliation: Neurochemistry and Biochemical Neuropharmacology Research Unit, Department of Biochemistry, University of Karachi, Karachi, Pakistan. aapa1@hotmail.com
authors.forename: Saida
authors.initials: S
authors.lastname: Haider
authors.forename: Nosheen
authors.initials: N
authors.lastname: Naz
authors.forename: Saima
authors.initials: S
authors.lastname: Khaliq
authors.forename: Tahira
authors.initials: T
authors.lastname: Perveen
authors.forename: Darakhshan J
authors.initials: DJ
authors.lastname: Haleem
mesh_terms: D006916:5-Hydroxytryptophan / Q000097:blood / Q000378:metabolism*; D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects; D001921:Brain / Q000378:metabolism*; D005737:Garlic; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D008568:Memory / Q000187:drug effects* / Q000502:physiology; D008517:Phytotherapy; D028321:Plant Preparations / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D014364:Tryptophan / Q000097:blood / Q000378:metabolism
chemical_list: D028321:Plant Preparations; D006897:Hydroxyindoleacetic Acid; D014364:Tryptophan; D006916:5-Hydroxytryptophan