screening model for learning and memory

Presented by
Mastan Naikwade, 2nd sem
Dept. of pharmacology and toxicology
PC/2017-X/167
5/18/2018 1

Introduction
Types of memory
Mechanism of Memory formation
Screening models
References
Contents
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Memory is our ability to encode, store, retain and subsequently recall information and past
experiences in the human brain. ... It is the ability to remember past experiences, and the
process of recalling previously learned facts, experiences, impressions, skills and habits.
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Upon weak stimulation By Strong StimulationUse it or loose it..!!
For Short-Term memoryFor long term memory 5/18/2018
6

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Screening models
Passive
Avoidance(in-vivo)
Spatial Memory(in-vivo
& in-vitro)
1. Step Down.
2. Step through.
3. Scopolamine
induced amnesia in
mice.
4. Ischemia induced
amnesia in gerbils.
1. Radial arm maze.
2. Morris Water maze.
3. Hesperidin and
Silibinin Ameliorate
Aluminum-Induced
Neurotoxicity.
4. Amyloid-β1–42
Oligomers induced
memory deficit.

PURPOSE AND RATIONALE
An animal(mouse or rat) spends most of the time close to walls and in corners. When placed on an
elevated platform in the center of rectangular compartment, it steps down immediately to the floor to
explore the enclosure and to approach the wall.
The term “passive avoidance” is usually employed to describe experiments in which the animal
learns to avoid a noxious event by suppressing a particular behavior.
1.Step down
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Species-
Swiss male albino mice (25-30 g).
Memory impairing drug- Phenytoin(25 mg/kg
p.o)
Standard drug- Piracetam(200 mg/kg p.o)
Familiarization(ani
mal is placed on
platform, released
after raising the
cylinder and latency
is measured. After 10s
of exploration, it is
returned to home
cage)
Learning(moving
down from platform
an unavoidable foot
shock applied-
50hz,1.5ma,1s and
animal returned to
home cage)
Retention test (24 h after
the learning trial the
animal is again placed on
the platform and the step-
down latency is measured.
The test is finished when
the animal steps down or
remains on the platform
(cut-off time: 60 s).
Procedure:-
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EVALUATION
The time of descent during the learning phase and the time during the retention test is
measured. Aprolongation of the step- down latency is defined as learning.
LIMITATION
The variability of this method is relative high, therefore, it is necessary to
test large groups of animals
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2.STEPTHROUGH
•This test uses normal behavior of mice and rats.
• These animals avoid bright light and prefer dim
illumination.
•It is widely used in testing the effects of memory active
compounds
PROCEDURE
Mice and rats of either sex are
used. The test apparatus consists
of small chamber connected to a
larger dark chamber via a
guillotine door.
In the acquisition trial the animal
is placed in the illuminated
compartment at a maximal
distance from the guillotine door,
and the latency to enter the dark
compartment is measured.
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Species-
Wistar/Sprague
-Dawley,
Swiss,Albino
Mice

The small chamber is illuminated
with a 7 W/12 V bulb. The test
animals are given an acquisition
trial followed by a retention trial
24 h later.
Animals that do not step through the door within a cut-off time: 90 s
(mice)or 180 s (rats) are not used. Immediately after the animal enters
the dark compartment, the door is shut automatically and an
unavoidable footshock (Footshock:1 mA; 1 s – mice; 1.5 mA; 2 s –
rat) is delivered.
The animal is then quickly removed (within 10 s)
from the apparatus and put back into its home cage.
The test procedure is repeated with or without drug.
The cut-off time on day 2 is 300 s (mice) or 600 s
(rats), respectively
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EVALUATION
The time to step-through during the learning phase is measured and the time during the retention test is
measured.
In this test a prolongation of the step-through latencies is specific to the experimental situation. An
increase of the step-through latency is defined as learning.
LIMITATION AND CRITICAL ASSESMENT
The variability of this method is relative high, therefore, it is necessary to test large groups of
animals.
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3.Scopolamine-inducedamnesiainmice
The administration of the antimuscarinic agent scopolamine to young human
volunteers produces transient memory deficits in animals.
Analogously, scopolamine has been shown to impair memory retention when given to mice
shortly before training in a dark avoidance task.
PROCEDURE
1.Five min after i.p. administration of 3 mg/kg scopolamine hydrobromide, each mouse is individually
placed in the bright part of a two-chambered apparatus for training.
2.After a brief orientation period, the mouse enters the second, darker chamber. Once inside the second
chamber, the door is closed which prevents the mouse from escaping, and a 1 mA, 1-s foot shock is
applied through the grid floor.
5.Aprolonged latency indicates that the animal remembers that it has been punished and,
therefore, does avoid the darker chamber.
3. The latency in entering the second darker chamber in untreated control animals is 250s,
whereas treatment with scopolamine reduces latency to 50 s.
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Species:-10 male Swiss albino mice weighing 26–
32 g in a one-trial, passive avoidance paradigm.

EVALUATION
Using various doses latencies after treatment with test compounds are expressed as percentage of
latencies in mice treated with scopolamine only.
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4.ISCHEMIA-INDUCEDAMNESIAIN GERBILS
Species- Male Mongolian gerbils(weighing
50–70 g)
1.Anesthetized by i.p. pentobarbital injection. Both common carotid arteries
are exposed through a ventral neck incision and occluded for 5 or 10 min
with miniature aneurysm clips.
2.In sham-operated controls, the common carotid arteries are exposed but
not occluded. Twenty-four hours after occlusion, each animal is placed in
the bright part of a light/dark-chambered apparatus for training.
3.Once inside the second chamber, the door is closed which prevents the
animal from escaping, and a 100 V, 2-s foot shock is applied through the
grid floor. The gerbil is then returned to the home cage.
Procedure
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4.The latency compared with sham-operated controls is decreased
depending on the duration of ischemia.
After drug treatment, an increase of latency in entering the dark
compartment indicates good acquisition.
Continued…..
Evaluation:
Using various doses a dose-dependent increase of latency can be found after
active drugs
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Effect of dexmedetomidine on
latency in the step-down
avoidance task under ischemic
conditions. (A) Sham-operated, (B)
ischemia-induction, (C) ischemia-
induction and 0.1 µg/kg
dexmedetomidine-treated, (D)
ischemia-induction and 1 µg/kg
dexmedetomidine-treated and (E)
ischemia-induction and 10 µg/kg
dexmedetomidine-treated groups.

1.Spatiallearningintheradialarmmaze
The rat uses spatial information provided by the distal cues in the room to efficiently
locate the baited arms. The radial arm-maze allows the study of spatial reference and
working memory processes in the rat.
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• PROCEDURE
Evaluation
The number of errors (entries to non-baited arms) are
counted during the session
1.The apparatus is a wooden elevated eight-arm radial
maze with the arms extending from a central platform
26 cm in diameter. Each arm is 56 cm long and 5 cm
wide with 2 cm high rails along the length of the arm.
2.Food pellets (reward) are placed at the end of the
arms. During the test, rats are fed once a day and
their body weights maintained at 85% of their free
feeding weight to motivate the rat to run the maze.
3.The session is terminated after 8 choices and the rat
has to obtain the maximum number of rewards with a
minimum number of errors.
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2.Spatiallearninginthewatermaze
A task was developed where rats learn to swim in a water tank to find an escape
platform hidden under the water.
Learning is reflected on the shorter latencies to escape and the decrease on the
length of the path to find the platform’
Species used:-Young Sprague-Dawley rats (3 months old)
PROCEDURE
1.The apparatus is a circular water tank filled to a depth of 20 cm with 25 °C water.
The tank is divided in four equal quadrants and a small platform is located in the
center of one of the quadrants
2.The rat is released into the water and allowed 60–90 s to find the platform.
2.
3.Animals usually receive 2–4 trials per day for 4–5 days until they escape onto the
platform. Well trained rats escape in less than 10 s.
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Evaluation
The latency to reach the escape platform is
measured during the training days
MODIFICATIONS OF THETEST
•In the “cue” version of the water maze, the
platform is clearly visible over the water and
allows the evaluation of the motor and
motivational aspects of the rat under study, as
the animals should easily find the visible
platform in 10–15s.
•To evaluate working memory processes in the
water maze, the rat can be trained to find a
new platform position and later its
performance is tested after a short delay
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HESPERIDIN AND SILIBININ AMELIORATE ALUMINUM-INDUCED
NEUROTOXICITY
Species - Male Swiss albino mice (weight 25–30 g).
procedure
AlCl3 (100 mg/kg/day) was
injected daily through oral gavage for 42 days
Concomitantly, hesperidin (50 and 100 mg/kg/day, p.o.) and silibinin (100 and
200 mg/kg/day, p.o.) was administered for 42 days in different groups.
The extent of cognitive impairment was assessed by
Morris water maze and novel object recognition test on the
43rd day.
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Six weeks treatment with AlCl3 caused cognitive impairment as indicated by an increase in the
retention latency time and reduction in the percentage of recognition.
AlCl3-treated group showed oxido-nitrosative stress as indicated by increase in the level of lipid
peroxidation, nitrite and depleted reduced glutathione, catalase activity in the hippocampus.
Evaluation
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NEUROTOXICITYAND MEMORYDEFICITSINDUCEDBY SOLUBLE LOW-MOLECULAR-
WEIGHTAMYLOID-Β1–42OLIGOMERS
• PROCEDURE
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1. After 1 week of recovery, awake and freely moving mice were
injected with 0.2 μg/μl of soluble Aβ1–42 oligomers
2. Five days after the last injection, mice were tested for hippocampus-
dependent spatial memory using a two-trial Y-maze task
3.Mice were assigned to two arms (the “start arm” and the “other arm”)
that they were allowed to explore ad libitum for 5 min, without access to
the third arm of the maze (the “novel arm”) blocked by an opaque door.
4. Mice were placed at the end of the same start arm and allowed to
explore ad libitum all three arms for 2 min
Evaluation
The amount of time spent in each of the arms was recorded
using EthovisionXT (Noldus).
Species:3- to 4-month-old
C57BL/6J wild-type

References:
 Choi IY, Hwang L, Jin JJ, Ko IG, Kim SE, Shin MS, Shin KM, Kim CJ, Park SW, Han JH, Yi JW.
Dexmedetomidine alleviates cerebral ischemia-induced short-term memory impairment by inhibiting the
expression of apoptosis-related molecules in the hippocampus of gerbils. Experimental and therapeutic
medicine. 2017 Jan 1;13(1):107-16.
 Jangra A, Kasbe P, Pandey SN, Dwivedi S, Gurjar SS, Kwatra M, Mishra M, Venu AK, Sulakhiya K, Gogoi
R, Sarma N. Hesperidin and silibinin ameliorate aluminum-induced neurotoxicity: modulation of
antioxidants and inflammatory cytokines level in mice hippocampus. Biological trace element research. 2015
Dec 1;168(2):462-71.
 Brouillette J, Caillierez R, Zommer N, Alves-Pires C, Benilova I, Blum D, De Strooper B, Buée L.
Neurotoxicity and memory deficits induced by soluble low-molecular-weight amyloid-β1–42 oligomers are
revealed in vivo by using a novel animal model. Journal of Neuroscience. 2012 Jun 6;32(23):7852-61.
 Narwal S, Saini DR, Kumari K, Narwal S, Singh G, Negi RS, Sarin RV. Behavior & pharmacological animal
models for the evaluation of learning & memory condition. Indo Global J Pharm Sci. 2012;2(2):121-29.
 Drug Discovery and Evaluation: Pharmacological Assays Editors: Vogel, Hans Gerhard (Ed.) 2008.
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screening model for learning and memory

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