clitoria ternatea (linn) root extract …...indian j physiol pharmacol 2001; 45 (3) :305-313...

Indian J Physiol Pharmacol 2001; 45 (3) : 305-313

CLITORIA TERNATEA (Linn) ROOT EXTRACT TREATMENTDURING GROWTH SPURT PERIOD ENHANCESLEARNING AND MEMORY IN RATS

KIRANMAI s. RAI*, K. DILIP MURTHY**, K. S. KARANTH***AND MUDDANNA S. RAO****

Departments of Physiology*, Anatomy****,K. M. c. Manipal - 576 119,

Department of Physiology**,I. C. H. S Manipal - 576 119

and

Department of Pharmacology***,K. s. l!egde Medicr;zl Academy,Deralkatte, Mangalore - 575 001

(Received on May 15, 2000)

Abstract: Neonatal rat pups (7 days old) were intubated with either 50mg/kg body weight or 100 mg/kg body weight of aqueous root extract ofClitoria ternatea (CTR) for 30 days. These rats were then subjected toopen field, two compartment passive avoidance and spatial learning (T-Maze) tests (i) immediately after the treatment and (ii) 30 days after thetreatment, along with age matched normal and saline control rats. Resultsshowed no change in open field behaviour, but showed improved retentionand spatial learning performance at both time points of behavioural tests,indicating the memory enhancing property of CTR which implicates apermanent change in the brain of CTR treated rats.

Key words: Clitoria ternateaspatial learning-T maze

passive avoidance open fieldlearning and memory

INTRODUCTION (1). Some of these herbal drugs reported toact on the nervous system include-Clitoriaternatea (2, 3), Acorus calamus, Centellaasiatica (3, 4, 5), Withania somnifera,Celastrus panniculatus, Guduchi and Areca."Medhya rasayana" a rejuvenating recipecontaining Clitoria ternatea is consideredwholesome for intellect (6).

In the Ayurvedic system, ofmedicine "Medhya drugs" -a group ofherbal medicines are known for theiractions on the nervous system. These"Medhya drugs" mentioned in Ayurvedictexts are said to improve mental abilities

*Corresponding Author

306 Kiranmai et al

Clitoria ternatea (commonly calledShanka pushpi) is a twining herb with whiteflowers resembling a conch-shell (2, 3).Extracts of Clitoria ternatea has been usedsince time immemorial to treat mentaldisorders since it has property of being agood nervine tonic (3). Our preliminarystudy on Clitoria ternatea root extractshowed a memory enhancing property inrats (7). Though Clitoria ternatea rootextract is claimed to improve learning andmemory (3) there are no experimental orclinical studies to show that this herb affectslearning and memory. Thus, this study wasdesigned to find the effect of Clitoriaternatea root extract treatment on thegeneral behaviour and learning and memoryin rats. Further, our aim was also to study,whether behavioural changes occurring inthese experimental rats were transient orpermanent. The present experiment wasdesigned on neonatal rat pups, since in rats,active brain growth occurs during preweaning and post weaning period (growthspurt period, 8).

METHODS

Aqueous root extraction

Fresh roots of Clitoria ternatea werecollected, cleaned, cut into small pieces andsunshade dried. It was then hand powdered.Dry powder was weighed and mixed withdistilled water at 1:10 ratio and boiled overa low flame for half an hour. It was thencooled and decanted. Residue was mixedwith distilled water (1:10) and boiled for 30minutes, cooled and decanted. The aboveprocedure was repeated twice. The clearsupernatant obtained each time wasdecanted and then centrifuged (3000 rpm

Indian J Physiol Pharmacol 2001; 45(3)

for 5 minutes) and the supernatant wasevaporated on low flame, to get a thick pastelike extract, which was later dried in anincubator at 37° C and the dry powder soobtained was stored in a dessicator.

Animals and experimental groups

Wistar rats provided with food and waterad libitum, maintained under 12 hours darkand 12 hours light cycle were used for theexperiments. Seven days old neonatal ratpups were divided into three groups. 1)Normal control (NC) -These rats remainedundisturbed in their home cage for 30 days.2) Saline control (SC) - These rats receivedorally, a known volume of saline each dayfor 30 days (period of intubation). 3) Clitoriaternatea root extract (CTR) treated groupof rats, were divided into two subgroups,receiving orally, either CTR 50 mg/kg orCTR-100 mg/kg, respectively, every day, for30 days.

Behavioural tests

All four groups of rats were subjected tothe following tests- a) open field behaviouraltest, b) two compartment passive avoidancetest and c) spatial learning test (T-Maze)-commencing from postnatal day 38 (i.e. aday after the last dose, early test). Theserats were later once again subjected to thesame tests on postnatal day 68 (i.e. 30 daysafter the last dose, delayed test) in order totest whether the behavioural changes, ifany, is transient or permanent.

a) Open field behaviour test

This test was carried out as explainedby Buresova 0 and Bures J (9). Open field


behavioural test apparatus consisted of alarge wooden box 100x100 em with 40 emhigh walls. The floor consisted of a blackpainted wire mesh grid dividing the fieldinto 25 equal squares 5 x 5 em with 16peripheral squares (PS) close to the walland a central squares (CS). A 100 watts bulbwas placed centrally, 5 feet above, for brightillumination.

The rat was placed in a corner of theapparatus and was allowed to explore theapparatus for 5 minutes. During this periodthe number of peripheral and centralsquares entered by the rat and the numberof boli of excreta excreted were counted.Incidences of expression of rearinggrooming/preening behaviours were alsonoted. Increase in the number of peripheralsquares entered and more time spent in theperipheral area was considered as anincrease in motor activity. Increased numberof central squares entered and more timespent in the centre of the field indicatesdecreased fear and anxiety and emotionaldisturbance.. Increased number of grooming(10), number of boli of excreta (9) anddecreased rearing (10) are the expressionsof emotionality, which are measures ofautonomic function in the animals.

b) Passive avoidance test

Modified procedure of Buresova 0 andBures J (9) was adopted.

The passive avoidance apparatusconsisted of a box/compartment with 50 x50 em grid floor and wooden walls of 35 cmheight. A 100 watts bulb placed 5 feet above,illuminated this box. A smaller darkcompartment 15x15x15 em, with electrified

Clitoria ternatea Enhances Memory 307

grid floor, connected to a constant currentstimulator, opened into this box on one side.A 6x6cm opening in the wall between thetwo boxes/compartments could be closedusing a transparent plexiglass sliding door.

On the first day of the test, each ratwas allowed to explore the two compartmentfor 5 minutes. On the second day latency toenter the dark compartment for the firsttime was noted for each rat. The learningsession was followed immediately. Theplexiglass door between the . twocompartments was closed and the rat wasconfined to the dark compartment. Threeinescapable electric foot shocks (50 Hz, 1.5mA, 1 sec) were delivered to the rat. Therat was then returned to its home cage.Retention performance of each rat wastested by noting the latency to enter thedark compartment after a period of 48 hoursand 30 days respectively. Increase in thelatency to enter the dark compartmentduring retention test (i.e. 48 hrs/30 days)after inescapable foot shock, was interpretedas good retention performance.

c) Spatial learning test (T.Maze test, 11)

To assess the spatial learning ability,rats were subjected to spontaneousalternation and rewarded alternation tests.

The T· Maze consisted of a start box15x12 em, a stem 35x12 em, a choice area15x12 cm and two arms 35x12 em each, atthe end of which were the goal areas 15x12cm each, containing the food pellets. Theside walls were 40 cm in height. A slidingdoor separated the stem, from the start box.'I'he T -maze was kept in a sound attenuatedroom.

308 Kiranmai et al

i) Spontaneous alternation test

Rats were starved for two days prior tothe test in order to motivate them for foodreward. Subsequently food was restricted sothat the body weight was maintained at 85%of pretest weight.

Rats were placed in the T-maze for 30minutes daily, for 2 days, to orient them tothe T -maze environment. During thesesessions 15 pellets of food (10 mg each) werekept in each goal area.

On the following 4 days, six trialswere given daily. In each trial, the ratwas placed in the start box and the dooropened, thus allowing it to enter into thestem and arms of the T -maze. After the ratate the pellet in the goal area, it wasreplaced back in the start box. In each trial,the arm chosen by the rat and numberof alternations made, were noted. Theinter-trial interval was one minute. The ratwas deemed to have entered into aparticular arm when it entered that armwith all its four limbs. Percentage bias wascalculated for each rat using the followingformula:

% bias = Total number of choices of more frequently chosen sidex100Total number of trials

More number of alternations and less %bias was considered as an index of improvedlearning ability.

ii) Rewarded alternation test

This test was done after completion ofspontaneous alternation test. Test consisted


of 6 trials/day, for four consecutive days.Each trial had two runs viz. forced run andchoice run. In the forced run, the rat wasforced to one of the arms by blocking theother arm and allowing it to consume thepellet there. In the choice run, the forcedarm was kept empty and pellet was placedin the opposite arm. Both the arms werefree for the rat to run. Now, the rat had toenter into the arm, opposite, to theforced arm, if it had to be considered as"correct response". The forced arm waspredetermined and it was same for all ratson any given day. It was changed onsubsequent days. Experiment was repeatedon 4 successive days. "Percentage of correctresponses" was calculated for each rat byusing the following formula:

% correct res nse = Total number of choices of correct response x 100po Total number of trials

Increase in mean % correct response wasconsidered as improved learning andmemory.

Statistics

Data obtained from the above tests wereanalysed by applying One Way ANOVAfollowed by post test (Dunnet test).

RESULTS

a) Open field test

Results of open field behaviour is shownin Table I and II. There was no statisticaldifference in any of the parameters studiedeither immediately after the treatment or30 days after the treatment.


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b) Passive avoidance test

Results of two compartment passiveavoidance retention performance is .shown in Fig. 1. The rats which receivedCTR100 mg/kg body weight per dayshowed very good memory retentionafter 48 hrs (77.94 ± 17.37 sec. in NCvs. 150.05 ± 7.99 sec. in CTR100,P<O.Ol). These rats also showedimproved memory retention, even30 days after treatment (27.78± 6.54 sec.in NC vs. 103.69 ±16.1 sec. in CTR100P<0.05).

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Fig. 1 : Two compartment passive avoidancetest performance (latency to enter darkcompartment) during early and delayed posttreatment periods, in control's and Clitoriaternatea root extract treated rats.

c) Spatial learning test (T-Maze test)

i) Spontaneous. alternation test

Table III shows the number ofalternations made by different groups of ratsduring spontaneous alternation test. Therewas no significant difference in total number

310 Kiranmai et al Indian J Physiol Pharmacol 2001; 45(3)

TABLE II: Open field test performance.

Groups No. of rearing No. of grooming No. boli of Excreta

Early Delayed Early Delayed Early Delayed

NC n=17 25.53±1.14 12.5± 1.86 4±0.39 5±1.13 0.41±0.21 1.5±0.8

SC n=24 19.71±1.41 15.5±2.7 4.79±0.42 5.86±0.74 0.04±0.04 1.88±0.64

CTR 50 n=20 15.75±1.05 10±2.22 3.45±0.29 9.44±2.59 0.5±0.21 O±O

CTR 100 n=22 22.86±1.68 16.2±2.5 3±0.32 3.3±0.7 1.09±0.33 0.3±0.3

Open field test performance (number of rearing, grooming and number of boli excreated) in openfield apparatus, during early (at postn at.al day 38) and delayed )at postnatal day 68) tests. each valuerepresents Mean ± SEM. There was no statistical signicance in any comparisons (ANOVA); NC=Normal Control;SC= Saline control; CTR 50/100=Clitroria ternatea root extract treated-50 or 100 mg/kg body weight per day.

TABLE III: Spontaneous alternation test-Total number of alternations.

GroupsTotal no. of alternations

Early test Delayed test

NC

SC

CTR 50

CTR 100

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n = 22

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12.46±0.61

13.55±0.67

14.32±0.5

11.38±1.45

11±1.11

16±0.55*

12.3±0.54

Total number of alternations during early (at postnatal day 38) and delayed (at postnatal day 68) tests. Eachvalue represents Mean ± SEM *P<0.05 NC Vs CTR 50 ANOVA, F = 5.609; (df = 82) NC = Normal Control;SC = Saline control; CTR 50/100 = Clitoria ternatea root extract -50 or 100 mg/kg body weight per day.

of alternations. among the different groupswhen tested immediately after the rootextract treatment. However, rats whichreceived 50 mg CTR/kg body weight per dayshowed slightly improved alternation whentested 30 days after the treatment(11.38 ± 1.45 in NC vs 16.00±0.55 in CTR50, P<0.05).

Mean % bias data is shown in Fig. 2.The rats that received 100 mg CTRlkg bodyweight per day showed significantly less %bias as compared to normal control ratswhen tested immediately after thetreatment (62.25 ± 1.87 III NC vs

70

.NCn-17

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Fig. 2: Spontaneous alternation test performance(Mean % bias) during early and delayed posttreatment periods, in controls and Clitoriaternatea root extract treated rats.


56.06 ± 1.12 in CTR100, P<0.05)and even,30 days after treatment (61.80 ± 5.32 in NCvs 53.64 ± 1.46 in CTR 100, P<0.05).

ii) Rewarded alternation test

Fig. 3 shows mean % correct responseof various groups of rats. CTR50 as well asCTR100 groups of rats showed increasedmean % correct response when tested onday 38 (67.89±3.64 in NC vs 80.7 ± 2.45 inCTR50, P<0.05, and 67.89 ± 3.64 in NC vs86.11 ± 2.14 in CTR100, P<O.OOl) Theimproved behaviour remained as such, evenon day 68 i.e after 30 days (59.37 ± 2.7 inNC vs 82.87 ± 2.73 in CTR50, P<O.OOl, and59.37 ± 2.7 in NC vs 83.75±3.43 in CTR100P<O.OOl).

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Fig. 3: Rewarded alternation test performance (Mean% correct response) during early and delayedpost treatment periods, in controls and Clitoriaternatea root extract treated rats.

DISCUSSION

The results of the present study revealedthat CTR root extract had memoryenhancing properties which had no or littleeffect on the general motor activity andother behaviours in rats. This memory


enhancing property was marked' in neonatalrats (which were in their brain growth spurtperiod) treated with CTR 100 mg/kg bodyweight for 30 days. Thus it appears thattreatment with CTR extract must havecertain permanent changes in the brain,which were responsible for the improvedlearning and memory.

This is the first report regarding,memory enhancing property of Clitoriaternatea aqueous root extract treatment,studied experimentally. The effect ofalcoholic extract of Clitoria ternatea plant(i.e. stem, leaves and flowers) on the CNShas been reported (12). Treatment withalcoholic extract of Clitoria ternatea plantreduced spontaneous motor activity,increased sedation, diminished alertnessand responsiveness to' acoustic, tactile andnociceptive stimuli, and significantlyprolonged time taken to traverse the watermaze .

The exposure to new learningexperiences (13), intracranial selfstimulation (14) and environment within thepyramid model (15) has been shown to alterthe cyto-architecture of brain regionsconcerned with learning and memory (i. ehippocampus). Fresh leaf extract of Centellaasiatica has been shown to improve learningand memory correlated with an increase indendritic arborization of amygdala andhippocampus (16,17). The synapse numbersin the regions of hippocampus and cingulatecortex, was shown to be affected, when therats were chronically undernourished (18)

Emotional behavior of the rat, is alteredby many factors such as toxins (19) andexposure to ultra sound (20). In the present

312 Kiranmai et al

study there was no significant difference innumber of rearing, grooming and numberof boli excreted and also in the generalmotor activity of rats, which weretreated with CTR, either immediatelyafter the treatment or 30 days afterthe treatment. This suggests that CTR hadno or very little effect on motor andautonomic nervous system of the rats. Thetreated rats appeared to be emotionallyundisturbed.

Results form passive avoidance and spatiallearning tests showed improved retention,increased percentage correct response andtotal number of alternations and decreased% bias in CTR treated rats. This suggeststhat CTR affects the brain structuresconcerned with learning and memory

Indian J Physiol Pharmacal 2001; 45(3)

namely hippocampus and amygdala (13, 21,22). These behavioral changes are relativelypermanent indicating that CTR brings aboutpermanent changes in the brain as reportedin earlier studies (13,14). It may also affectthe biosynthesis of neurotransmitters likeacetylcholine, which has been implicated inthe process of learning and memory (23).On the other hand, CTR may also inducelong term potentiation. However, thesemorphological, neuro-physiological andneuro-chemical changes needs to beinvestigated.

We conclude that, Clitoria ternateaaqueous root extract treatment of neonatalrats, enhances their memory, which appearsto be due to permanent changes, in thebrain of these rats.

REFERENCES

1. Sharma P. In Drauyaguna Vignana 1998; 2:3-29.

2. Warrier PK. Indian medicinal Plants 1994;2: 129-132.

3. Sivaranjan VV, Indira Balachandran. Ayuruedicdrugs and their plant sources 1994; 425-428.

4. Dash PK, Mistry IV, Rao AR Patel KS. Ayurueda1996; 12-15.

5. Sathyavathi GV, Gupta AK, Tandon M. MedicinalPlants of India 1976; VOl.1

6. Sharma RK, Bhagwan Dash. In Caraka Samhitha1996; VOL III: 46

7. Rai KS, Rao MS, Karanth KS, Murthy KD. Clitoriaternatea enhances learning and memory-anexperimental study on rats. Abstract. In Souuenierof International Congress on Frontiers inPharmacology and Therapeutics in 21" century.1999; 121.

8. Dobbing J, Sands J. Annotation. Comparativeaspects of the brain growth spurt. Early HumanDeu. 1979; 3: 79-83

9. Buresova 0, Bures J. Learning and memory. InTechnique and basic experiments for the study ofbrain and behauiour . Bures J, Buresova 0and Huston 1'. (Eds), Elsevier, Amsterdam. 1976;91-162.

10. Sutton RE, Koob GF, Moal M Le, Rivier J, Vale W.Corticotropin releasing factor producesbehavioural activation in rats. Nature 1982; 297:331-333.

11. Dunnett SB, Low WG, Iversen SD, Stenevi U,Bjorklund A. Septal transplant restore mazelearning in rats with fimbria fornix lesions. BrainRes 1982: 15: 335-348

12. Kulkarni C, Pattanshetty JR, Amruthraj G. Effectof alcoholic extract of Clitoria ternateaLinn on central nervous system in rodents.Indian journal of Expt Biology. 1988; 26:957-960.

13. Mahajan DS Desiraju T. Alterations of dendriticbranching and spine densities of-hippocampal CA3pyramidal neurons induced by operant conditioningin the phase of brain growth spurt. Expt Neurol1988; 100: 1-15.


14. Rao BSS, Desiraju T, Raju TR. Neuronalplasticity induced by selfstimulation rewardingexperiences in rats-a study on alteration indendritic branching in pyramidal neurons ofhippocampus and motor cortex. Brain Res 1993;627: 126-224.

15. Bharathi H, Rao MS, Murthy KD. Pyramidenvironment enhances learning and memory-abehavioural and morphological study. Abstract. Insouvenier International congress on Frontiers inPharmacology and Therapeutics in 21" century.1999; 82.

16. Rao MKG, RaoMS, Karanth KS, Rao GM. Effectof Centella asiatica extract on rat CNS-a functinaland morphological correlation. Abstract InSouvenier National conference of IndianPharmacological Society 1998; 74.

17. Rao MKG, Rao MS, Rao GM. Centella asiaticaextract enhances learning -correlation withhippocampal structural changes. Abstract. Insouvenier International Congress on Frontiers inPharmacology and Therapeutics in 21" century.1999; 120.


18. Dilip Murhty K, Desiraju T. Synapses in developingcingulate and hippocampal cortices in undernourishedrats. Neuro Report 1991; 2: 433-436.

19. Lakshmana MK, Raju TR. Endosulfan inducessmall but significant changes in the level ofnoradrenaline, dopamine and serotonin indeveloping rat brain and deficits in operantlearning performance. Toxicology 1994;91:139-150.

20. Uma Devi P, Suresh R, and Hande MP. Effect offetal exposure to ultra sound on behaviour of adultmouse. Radiation Research 1995; 141: 314-317.

21. Stephen Maren. Long term potentiation in theamygdala: a mechanism for emotional learning andmemory. Trends in Neuroscience 1999; 22:561-567.

22. 0' Keefe J, Nadal L. The hippocampus as acognitive map. Oxford University Press (Clarendon)London/ New York 1978.

23. Bartus RT, Dean RL, Beer B, Lippa AS. TheCholinergic hypothesis of geriatric memorydysfunction. Science 1982; 217: 408-417.

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