EFFECT OF CONVULVULUS PLURICAULIS CHOISY. ON LEARNING BEHAVIOUR AND MEMORY ENHANCEMENT ACTIVITY IN RODENTS

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1 EFFECT OF CONVULVULUS PLURICAULIS CHOISY. ON LEARNING BEHAVIOUR AND MEMORY ENHANCEMENT ACTIVITY IN RODENTS ALOK NAHATA* AND V.K. DIXIT Natural Product Research Laboratory, Department of Pharmaceutical Sciences, Dr. H. S. Gour Vishwavidyalaya, Sagar (MP) Shankhpushpi Shankhpushpi is an important indigenous drug, reputed as an alternative, laxative and brain tonic. The drug consists of the whole dried herb identified as Evolvulus alsinoides Linn. Family : Convulvulaceae Convulvulus pluricaulis Choisy. Family : Convulvulaceae Clitorea ternatea Linn. Family : Papilionaceae Canscora decussata Schultz. Family : Gentianaceae 1

2 Convulvulus pluricaulis Choisy. Family: Convulvulaceae Synonym: Convulvulus microphyllus Sieb. Morphological Characters The stem of this procumbent herb is woody at the base and leaves are linear,elliptical, subsessile having trichomes on both the surfaces. It is a prostate herb with white or pale-pink flowers.the flowers are short, axillary, solitary or 2-3 together. Corolla is funnel shaped; limb 5 plainted, subentire stamens included or exserted, filaments filiform. Phyllotaxy, pentastichous. Phytoconstituents Major chemical constituents of the plant are scopoletin, kaempferol-3 glucoside and 3, 4 dihydroxycinnamic acid. CH O 3 Two uncharacterized bases: base A (C 5 H 11 N0 2 ),base B (C 5 H 9 NO 2 ), and an alkaloid shankhpushpine has been isolated. HO O Scopoletin O Pharmacological Activity and Uses Memory potentiating and cognition enhancer. Antidiabetic and tranquilizing properties. Hypolipidaemic and useful in hyperthyroidism. The fresh juice of the herb is used as nervine tonic in cases of epilepsy, insanity and nervous debility. It is useful as an antianxiety agent and a brain tonic. 2

3 MATERIALS AND METHODS Plant Material and Extraction Aerial parts of Convulvulus pluricaulis were used. The powdered drug was subjected to ethanolic extraction. The ethanolic extract was suspended in distilled water and fractionated with ethyl acetate to get the ethyl acetate soluble fraction and the aqueous fraction. These fractions were utilized for the neuropharmacological investigation. Animals Sprague-dawley rats ( g) of either sex were used for the study. The animals were housed in groups of six in polypropylene cages, under standard laboratory conditions of temperature (25±2oC), lighting ( h) and relative humidity (50±5%). The animals had free access to standard pellet chow (Brooke Bond-Lipton, India) and water. The animals were acclimatized for a period of minimum 7 days. Experiments were conducted between 0900 and 1400 hrs. The experimental protocol was approved by the Institutional Animals Ethics Committee (IAEC) and care of laboratory animals was taken as per CPCSEA guidelines (Reg. No. 379/01/ab/CPCSEA). Drugs Scopolamine butyl bromide (SBB) used in the study. SBB was dissolved in normal saline for i.p. injection Administration of the extracts Suspensions of the ethanolic extract and its ethyl acetate and aqueous fractions were prepared in distilled water using Tween-80 (0.2% v/v) as the suspending agent. The extracts were administered in a dose of 100 and 200 mg/kg to rats by oral route, 45 min before the test procedures. Control groups were given only the vehicle (0.2% v/v Tween-80 solution) in volume equivalent to that of the plant extracts. Pharmacological Screening Parameters used to assess effects on learning and memory: Inhibitory (Passive) avoidance tests Scopolamine induced amnesia in rats Active Avoidance Tests Two compartment shuttle box 3

4 Effect of Convulvulus pluricaulis Choisy. on Scopolamine Induced Amnesia Effect of Convulvulus pluricaulis Choisy. on the % avoidance response in the Shuttle box avoidance paradigm % Avoidance Response Vehicle CPEA100 CPEA200 CPAqs100 CPAqs200 Training Trial Retention Trial-48 hrs Retention Trial-24 hrs Retention Trial-7Days 4

5 RESULTS AND DISCUSSION In the present study, antiamnesic effects of Convulvulus pluricaulis on scopolamine induced amnesia were successfully demonstrated throughout the study. Administration of scopolamine produced amnesia as seen from the reduction in the number of avoidance responses. However, continued treatment of CP extracts produced better retention and recovery in a dose dependent manner than the vehicle treated animals. In the shuttle box avoidance paradigm of our study, a significant increase in the %avoidance response was observed in the groups receiving the ethanolic extract, the ethyl acetate and aqueous fractions of CP as compared to the vehicle. The doses of 200 mg/kg of the drugs were found to be more potent indicating the dose dependent action of the drugs on cognitive functions and memory. Thus, it was concluded that CP holds sufficient calibre to be categorized as a memory enhancing agent in rodents in the laboratory models employed Scopolamine induced amnesia in rats This activity was performed using the Cook and Weidley's pole climbing apparatus. Rats were initially trained to escape the shock by climbing onto the pole, i.e. the shock free zone. During each of the initial trials the rats were allowed to explore the apparatus for 10 s. This was followed by a shock for 10 s. Only those rats, which were sensitive to the shock and could climb the pole were included in the study. The animals were divided into eight groups with six animals per group. Group I received the vehicle only. Group II received a single dose of scopolamine butyl bromide on day 9 while group III-VIII received the extracts (100 and 200 mg/kg p.o.). The ethanolic extract, ethyl acetate and aqueous fractions (100 and 200 mg/kg p.o.) were administered for a period of 7 days following which the training trial (TT) was conducted. Twenty four hours later, on 8th day, a relearning trial was conducted and the number of ARs in the 10 trial sessions was noted. On day 9 of the experiment, after attaining complete training, all the animals except the control, were treated with a single dose of scopolamine butyl bromide (SBB) (0.3 mg/kg i.p.), 30 minutes before the administration of the extracts. Control group received the vehicle alone. Training schedule was continued further with daily dosing of the extracts till 15 days. 5

6 Active Avoidance Tests Two compartment shuttle box The animals were trained in an active avoidance paradigm in a 25 cm x 25 cm x 40 cm shuttle box with a buzzer located at the midline on the lid of the box and floor consisting of the stainless steel grid bars. The box was divided into two equal compartments by a wood panel with an 8 cm x 7 cm hole in the middle (Leite, 1978). The conditioned stimulus (CS) was a light source and the buzzer for 10 seconds, followed by an unconditioned stimulus (US) i.e. an electric shock for 2 seconds. An avoidance response was recorded when animal avoided the US by crossing to the unelectrified dark compartment within 10 seconds after the onset of CS. The experiment continued for 14 days. The rats were divided into seven groups of six rats per group. Six groups received graded doses of the extracts (ethanolic extract and its ethyl acetate and aqueous fractions, 100 and 200 mg/kg p.o.) while the remained group received vehicle (0.2% v/v Tween-80) to serve as control. The avoidance response (AR), characterized by escape to the adjoining "safe" compartment during conditioned stimulus, was noted. % AR for 30 trials was computed for each animal. Retention trials were conducted 24 hours (RT-1), 48 hrs (RT-2) and 7 days (RT-3) after the initial trials....thanks 6