Planta Med 2008; 74(5): 485-490
DOI: 10.1055/s-2008-1074494
Pharmacology
Original Paper
© Georg Thieme Verlag KG Stuttgart · New York

A Time Course Analysis of Systemic Administration of Aqueous Licorice Extract on Spatial Memory Retention in Rats

Mohammad Sharifzadeh1 , Fazel Shamsa2 , Somayeh Shiran1 , Mohammad H. Karimfar3 , Abdol H. Miri3 , Hassan Jalalizadeh2 , Shervin Gholizadeh1 , Fatemeh Salar1 , Kaveh Tabrizian1
  • 1Department of Toxicology-Pharmacology and Center of Excellence of Toxicology, Pharmaceutical Sciences and Medicinal Plants Research Centers, Faculty of Pharmacy, Tehran University of Medicinal Sciences, Tehran, Iran
  • 2Department of Medicinal Chemistry, Faculty of Pharmacy, Medical Sciences, University of Tehran, Tehran, Iran
  • 3Faculty of Pharmacy, Zabol University of Medical Sciences, Iran
Further Information

Publication History

Received: August 2, 2007 Revised: February 20, 2008

Accepted: February 26, 2008

Publication Date:
10 April 2008 (online)

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Abstract

In the present study, the time course of the effects of Glycyrrhiza glabra L. (Leguminosae) aqueous extract (GE), administered systemically to rats, on the spatial memory retention in the Morris water maze was investigated. The dose of glycyrrhizin (GL), i. e., 0.5, 2.5 and 5 mg/mL in daily water intake of GE was administered to three groups of rats. The first, second and third groups received GE for 1, 2 and 4 weeks, respectively (each group included 3 subgroups). Three additional control groups of animals received only tap water during the same periods of time. After terminating the treatments, all animals were trained for four days; each day included one block and each block contained four trials. Test trials were conducted 48 h after the completion of the training period. Nicotine (1 μg/side) was infused into the CA1 region of the hippocampus as a positive drug control. GE treatment decreased both escape latency and traveled distance, but not swimming speed, compared with control, suggesting significant spatial memory retention enhancement by GE. Statistical analysis did not show any significant difference between GE-treated animals and the nicotine group in escape latency and traveled distance. At the end of the testing trials plasma samples were collected and the concentrations of glycyrrhetinic acid (GA) as a major metabolite of GL were measured in the different groups of treated rats. The maximum concentration was observed after four weeks of GE administration at 5 mg/mL of GL. These results showed that the enhancement effect of GE on spatial memory retention does not correlate with GA blood levels.

Abbreviations

Ach:acetylcholine

ChAT:choline acetyltransferase

COX:cyclooxygenase

CREB:cAMP response element binding protein

GE:Glycyrrhiza glabra aqueous extract

GA:glycyrrhetinic acid

GL:glycyrrhizin

NSAIDs:non-steroidal anti-inflammatory drugs

PKA:protein kinase A