4. Introduction
Rats frequently used as an animal model in
psychopharmacological research
How comparable are they? (Patterson-Kane, Hunt & Harper, 1999).
People: everyday novel objects
Standard rats: always same environment
Enriched rats (with novel objects) better?
5. 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)
6. 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?
7. Open Field test (Hall, 1934)
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.
8. Morris water maze (Morris, 1981)
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.
9. Object Recognition task
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)
10. Scopolamine
Cognitive impairing drug, blocks muscarinic receptors
Animal 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.
11.
12. Methods
36 Male Wistar
Rats
18 Standard 18 Enriched
condition Condition
13. From six weeks of age placed in
enviroment
Tests started with 12 weeks
Used to human contact
Reversed light-dark cycle: lights on from
19:00-7:00
Unlimited access to food and water
21 C 1 C, humidity 45%-55%
14. Standard
Three rats per cage six cages
40cm long x 20cm high x 25cm wide
Objects
Cardboard tube
Wooden stick
Sawdust bedding
16. Enriched
Two large cages with nine rats each
150cm long x 80cm high x 90cm wide
Environment changed and cleaned every week
Novel stimuli
Objects: PVC pipes, treadmills, brick stones, metal grid,
rope, wood sticks, different types of nesting material.
17. Tests we used:
Open field test
Anxiety behaviour
Morris water maze
Learning
Object Recognition task (novel object preference task)
Memory
18. Open field
Square box: 1m x 1m, grey floor
Tested four days in a row, day 4 had novel object
Five minutes exploration time
Measurements
By computer programme (EthoVision)
Distance moved, time near walls, time in centre, time in
corner
By human
Rears, leans, boli
19. Morris water maze
Large water tank: 122cm ø, 80cm height
Small platform placed 40cm from wall and 1cm below
water surface
Four different starting positions
Acquistion trial: 4 days in a row, 4 trials/day
Probe 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
20. Object Recognition task
Rats placed in round box, 1 transparent side
3 minutes exploration time each trial
Trial1: two similar objects
Trial2: one familiar object (like in trial1) and one new object.
Mug, jar, small bottle, cone
No medication
One hour delay
Twenty-four hour delay
With medication
One hour delay cognitive impairing drugs
27. Rears
There was only a group
effect between leaning
and distance travelled.
The standard rats had a
higher distance moved
and number of leans.
28. Analysis of the open-field (day 4)
Independent Measure Group Standard Enriched
variable
Distance travelled Anxiety/exploratory t= 5.03, df= 34, p < M= 1675.41, SD= M= 1218.90, SD=
behaviour .01 156.86, N=18 351.74, N= 18
Time in centre of Anxiety t= 2.12, df= 34, p < M= 50.60, SD= 13.07, M= 35.44, SD= 27.32,
field .05 N= 18 N= 18
Time in corners Anxiety n.s. M= 31.98, SD= 7.71, M= 54.51, SD= 26.19,
N=18 N= 18
Thigmotaxis/Time at Anxiety n.s. M= 60.81, SD= 10.37, M= 54.07, SD= 17.59,
wall N=18 N=18
Time spent at novel Exploratory n.s. M=6.61, SD= 5.45, N= M= 5.98, SD= 5.73,
object behaviour 18 N=18
Leaning Exploratory n.s. M= 19.42, SD= 5.72, M= 16.94, SD= 4.35,
behaviour N=18 N= 18
Rearing Exploratory n.s. M= 14.49, SD= 6.87, M= 16.37, SD= 5.71,
behaviour N= 18 N= 18
Boli Anxiety n.s. M= 3.61, SD= 3.26, M= 2.28, SD= 2.80,
N= 18 N= 18
29. Distance Moved
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
Time in Centre have spend more time in
the centre of the open
field.
30. Morris water maze
Acquisition trial
Acquisition trial Morris water maze (MWM)
Independent Measure Day Group Interaction
variable
Distance moved F(5,102) = 98.189, F(1,34) = 5.036, n.s.
p<0.001 p=0.031
Escape latency Learning F(3,102) = 78.374, n.s. n.s.
p<0.001
Mean velocity F(5,102) =7.868, n.s. n.s.
p<0.001
36. Object recognition task
No medication: • Effect of delay:
F(1,33) =24.348, P<0.001
• Group effect:
F(1, 33) = 5.133, P<0.05
D2 value is time spend at novel
object minus the time spend at No effects on total
old object corrected for exploration time or
exploration time preference for the left
or right object
37. Scopolamine
D2 Value
No effect on group:
F (1, 99) = 0.189, p=0.665
Dose effect:
F (2, 99) = 13.961, p<0.01
38. Exploration time trial1 (E1):
Group (n.s.):
F(1,98)= 1.720, p=0.193
Dose effect:
F(2,98)=3.111, p=0.049
Exploration time trial2 (E2):
Group (n.s.):
F(1,99) = 1.715. p=0.193
Dose:
F(2,99)= 6.602, p=0.002
39. Conclusions
Open 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
40. 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
41. 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.
42.
43. 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.
44. 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.
45. 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%).
46. Types of enrichment and standard conditions (Simpson & Kelly,
2011).
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).
Different combinations in the literature
47. 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.
48. 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.
