John BirraneMonique Peeters

ContentsIntroductionMethodsResults Discussion

IntroductionRats frequently used as an animal model in

psychopharmacological researchHow comparable are they? (Patterson-Kane, Hunt & Harper,

1999).People: everyday novel objectsStandard rats: always same environment

Enriched rats (with novel objects) better?

Enriched environment?Larger group of animals (Hamm, Temple, O’Dell, Pike &

Lyeth, 1996; Wainwright et al., 1993)More room to move arround (Arai & Feig, 2010; Hamm et

al., 1996; Wainwright et al., 1993).Lots of different object, stimulating all senses (Bennet et

al., 1964; Hamm et al., 1996)

Advantages enriched environment

More dendritic arborisation, neurogenesis, glial cells and improved learning (Kempermann, Kuhn, & Gage, 1997).

More synaptic plasticity (Rampon et al., 2000).The best way to investigate these advantages is the

performance on different tasks (Cao, Huang, and Ruan, 2008).

Effect on pharmacological interventions?

Measures anxiety and exploratory behaviour (Wainwright et al., 1993).

The field is divided into different areas: wall, corner and centre

Measures: behaviour and time spend in different areas open field.

Anxiety: more time in corners and near wall, low distance moved, more boli (Walsh & Cummins, 1976)

Exploratory behaviour: Number of rears and leans, and high distance moved.

Open Field test (Hall, 1934)

Measures spatial learning and memory (Morris, 1981)Circular tank, filled with water, with a platform placed

beneath water surface (Buccafusco, 2009).Rats will find the platform faster everyday regardless of

starting position.Measures: Swimming speed, distance moved, time in the

zone of the platform.Probe trials: no platform, check whether rats still know

the location of the platform.

Morris water maze (Morris, 1981)

AKA Novel object preference task (Mumby, Gaskin, Glenn, Schramek & Lehmann, 2002)

Two trails: one trial with two similar objects and one trial with an old and a new object (Mumby et al., 2002)

Rats have preference for novel object (Dix & Aggleton, 1998; Ennaceur & Delacour, 1988)

Looking at novel object correlates with memory of the familiar objects (Ennaceur & Delacour, 1988)

Object Recognition task

Cognitive impairing drug, blocks muscarinic receptorsAnimal model of Alzheimer’s disease

How will the environment influence the effect of scopolamine on memory?

Hypothesis: For enriched rats more scopolamine is needed to achieve a memory impairing effect.

Scopolamine

Methods

18 Standard condition

18 Standard condition

18 Enriched Condition

18 Enriched Condition

36 Male Wistar Rats

36 Male Wistar Rats

From six weeks of age placed in enviroment

Tests started with 12 weeksUsed to human contactReversed light-dark cycle: lights on from

19:00-7:00Unlimited access to food and water21°C ±1°C, humidity 45%-55%

StandardThree rats per cage six cages40cm long x 20cm high x 25cm wideObjects

Cardboard tubeWooden stick

Sawdust bedding

Enriched

Picture by Martina

EnrichedTwo large cages with nine rats each150cm long x 80cm high x 90cm wideEnvironment changed and cleaned every week

Novel stimuliObjects: PVC pipes, treadmills, brick stones, metal grid,

rope, wood sticks, different types of nesting material.

Tests we used:Open field test

Anxiety behaviourMorris water maze

LearningObject Recognition task (novel object preference task)

Memory

Open fieldSquare box: 1m x 1m, grey floorTested four days in a row, day 4 had novel objectFive minutes exploration time

MeasurementsBy computer programme (EthoVision)

Distance moved, time near walls, time in centre, time in corner

By humanRears, leans, boli

Morris water mazeLarge water tank: 122cm ø, 80cm heightSmall platform placed 40cm from wall and 1cm below

water surfaceFour different starting positionsAcquistion trial: 4 days in a row, 4 trials/dayProbe trial: day 3 (trial nr 5) and day 5 (trial nr 1)Reversal trials (other platform location): day 5 and 6, 4

trials/day EthoVision is used for the measurements

Object Recognition taskRats placed in round box, 1 transparent side3 minutes exploration time each trial Trial1: two similar objects Trial2: one familiar object (like in trial1) and one new object.Mug, jar, small bottle, coneNo medication

One hour delayTwenty-four hour delay

With medicationOne hour delay cognitive impairing drugs

Object recognition task (2)ScopolamineThree doses: injected 1ml/kg

0.00mg/ml (saline=control) 0.00 mg/kg0.03mg/ml 0.03 mg/kg0.30mg/ml 0.30mg/kg

Subcutaneous30 minutes before first trialDouble blind

Object Recognition task (3)Short Movie (or at least some pictures)

Statistical Analysis Open field Day 1-3 split-plot Day 4 independent samples t-testMorris water maze Acquisition split-plotProbe independent samples t-testReversal split-plotObject recognition taskNo medication: split-plot Scopolamine: univariate BS ANOVA

Open Field: Days 1-3

Independent variable

Measure Day Group Interaction

Distance travelled Anxiety/exploratory behaviour

F(2,68)= 23.617, p<0.001

F(1,34)= 30.500 p<0.001

F(2,68)= 7.490, p=0.001

Time in centre of field

Anxiety n.s. n.s. F(2,68)= 3.553, p <0.05

Time in corners Anxiety n.s. n.s. n.s.

Thigmotaxis/Time at wall

Anxiety n.s. n.s. n.s.

Leaning Exploratory behaviour

n.s. F(1,34) = 10.400, p<0.05

n.s.

Rearing Exploratory behaviour

F(2,68)= 4.181, p=0.019

n.s. n.s.

Boli Anxiety F(2,68) = 8.108, p=0.001

n.s. n.s

Distance Moved

Time in Centre

Leaning

Boli

Rears

There was only a group effect between leaning and distance travelled. The standard rats had a higher distance moved and number of leans.

Analysis of the open-field (day 4)

Independent variable

Measure Group Standard Enriched

Distance travelled Anxiety/exploratory behaviour

t= 5.03, df= 34, p < .01

M= 1675.41, SD= 156.86, N=18

M= 1218.90, SD= 351.74, N= 18

Time in centre of field

Anxiety t= 2.12, df= 34, p < .05

M= 50.60, SD= 13.07, N= 18

M= 35.44, SD= 27.32, N= 18

Time in corners Anxiety n.s. M= 31.98, SD= 7.71, N=18

M= 54.51, SD= 26.19, N= 18

Thigmotaxis/Time at wall

Anxiety n.s. M= 60.81, SD= 10.37, N=18

M= 54.07, SD= 17.59, N=18

Time spent at novel object

Exploratory behaviour

n.s. M=6.61, SD= 5.45, N= 18

M= 5.98, SD= 5.73, N=18

Leaning Exploratory behaviour

n.s. M= 19.42, SD= 5.72, N=18

M= 16.94, SD= 4.35, N= 18

Rearing Exploratory behaviour

n.s. M= 14.49, SD= 6.87, N= 18

M= 16.37, SD= 5.71, N= 18

Boli Anxiety n.s. M= 3.61, SD= 3.26, N= 18

M= 2.28, SD= 2.80, N= 18

Distance Moved

Time in Centre

There was only a group effect in the distance moved and time spend in centre. The standard rats had again a higher distance moved, and they have spend more time in the centre of the open field.

Morris water mazeAcquisition trial Morris water maze (MWM)

Independent variable

Measure Day Group Interaction

Distance moved F(5,102) = 98.189, p<0.001

F(1,34) = 5.036, p=0.031

n.s.

Escape latency Learning F(3,102) = 78.374, p<0.001

n.s. n.s.

Mean velocity F(5,102) =7.868, p<0.001

n.s. n.s.

Acquisition trial

Distance moved Mean Velocity

Time in zone

Independent samples t-tests

Zone 0-60 seconds 0-30 seconds 30-60 seconds

North n.s n.s. n.s.

East n.s n.s n.s.

South n.s. n.s. n.s.

West t(34) = 2.565, p<.05 t(34) = 3.044 , p<.005 n.s.

Platform zone t= -.2.24, df= 34, p < .05

t= 2.37, df= 34, p < .05 n.s.

Random zone n.s. n.s. n.s.

Probe trial

Time in zone platform vs time in random zone

Time in zone West

Reversal trial (new platform location)

Reversal trialsIndependent variable Measure Day Group

Distance Moved F(1,34) = 17.939, p<0.001

n.s.

Mean Velocity F(1,34) = 13.680, p=0.001

n.s.

Escape latency (reversal)

Learning F(1,34) = 24.644, p<0.001

n.s.

Distance moved Time in zone

Mean velocity

Object recognition taskNo medication:

D2 value is time spend at novel object minus the time spend at old object corrected for exploration time

• Effect of delay:F(1,33) =24.348, P<0.001

• Group effect:F(1, 33) = 5.133, P<0.05

No effects on total exploration time or preference for the left or right object

ScopolamineD2 ValueNo effect on group:F (1, 99) = 0.189, p=0.665

Dose effect:F (2, 99) = 13.961, p<0.01

Exploration time trial1 (E1):Group (n.s.): F(1,98)= 1.720, p=0.193Dose effect: F(2,98)=3.111, p=0.049

Exploration time trial2 (E2):Group (n.s.):F(1,99) = 1.715. p=0.193Dose:F(2,99)= 6.602, p=0.002

ConclusionsOpen field:

• Standard rats moved more on all four days• Enriched rats spent more time in corners of open

field• Leans and rears increase over time• Number of defeciations decline

Morris water maze:• Standard rats moved more• Decline in distance moved over the days on both

groups• Enriched rats spent more time in the west zone and

the zone of the platform during probe trials

Novel object preference task:• Enriched rats have a stronger preference for the

novel object after 24 hours delay (no medication)• With scopolamine there was a strong effect of the

dose, but no effect between groups on the exploration time and the preference for the novel object.

Open field results: Habituation the key?

Crusio and Schwegler (1987) and Crusio (2001) negatively correlate increased intra and infra hippocampal mossy fibre (IIHMF) projections with exploration.

Denenberg (1969) carried out a factor analysis of open field behaviour and found that increased ambulation was linked to anxious behaviour on only the first day. Indicative of the opposite for subsequent days.

Problems with this interpretation...

1. Some of these experiments conducted on mice... Wishaw and Tomie (1996) claim that rats and mice are comparable for a range of behavioural tests (as long as they don't involve water!). Neurobiological differences may exist though...

2. Meshi et al. (2006) demonstrated that behavioural differences caused by EE were not due to neurogenesis observed in van Praag's experiments.

The importance of exercise for enrichment

(a,f) = controls(b,g) = learner(c,h) = swimmer(d,i) = runner(e,j) = enrichment

In this experiment, enrichment had no effect on proliferation, but exercise did.

Enrichment did affect the survival of the newborn cells positively (85% vs. 56%).

Types of enrichment and standard conditions (Simpson & Kelly, 2011).

Different combinations in the literature

Social or physical enrichment? Both?

Dissociable effects?

Standard housing conditions of our rats did feature some physical enrichment (stick, cardboard tubes) along with moderate social enrichment (two litter-mates).

Perhaps standard rats were too enriched...

Lots of research in the literature features singly housed rats as controls. This deprivation state not a suitable control.

However, our results were not entirely anomalous. MWM performance reflected previous research in that enriched housing led to faster acquisition and more time spent in PZ during probe trial.

Performance in the ORT

No significant difference was observed between STD and EE rats in d2. There was a significant effect for dose at the lower dose, however.

Has scopolamine outlived its usefulness? Klinkenberg and Blokland (2010) affirm that scopolamine is an effective amnestic drug. However, dissociating its peripheral from its CNS effects can be challenging.

Any difference we would hope to observe between groups would have to be mediated through central nervous effects. But peripheral effects would not cause distinct differences in discrimination between groups.

QUESTIONS?

THANK YOU!!