Download - Screening of antianxiety drugs
In vivo methods Methods based on unconditioned
(spontaneous) response:o Exploratory activity
Elevated plus-mazeWater maze test Light-dark model (two compartment box)
Staircase explorationo Social behaviour
Social interactionIsolation induced aggressionAnticipatory anxiety in mice
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Methods based on conditioned (learned) response:oConflict models
Vogel punished drinking/ Vogel’s lick conflict model
Chemical induced methodmCPP induced anxiety in rats
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Elevated Plus Maze Test
o Most widely used method; male mice/rats used.
o For selective identification of anxiolytic and anxiogenic drugs
o Anxiolytics –decrease anxiety – increase open arm exploration time
o Anxiogenics – decrease open arm exploration time.
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o 2 open arms and 2 closed arms of 50 x 10 x 40cm dimensions
o Open roof arrangement
o Two open arms are opposite to each other.
o Maze elevated at 50cm height above the ground.
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Experimental Design
• Group I : control• Group II : standard • Group III : test treated with dose
x • Group IV : test treated with dose
2x ….
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Animals were allowed to explore in the maze for 5 min. Observations will done from adjacent room via remote TV camera.
Parameters Measured During Next 5 minutes:
o time spent in the open arms
o entries into the open arms
o time spent in the closed arms
o entries into the closed arms
o total arm entries8
Evaluation of results:o Motor activity and open arm
exploratory activity determined.o Values of treated groups expressed as
% of control values.o Benzodiazepines and valproate –
decrease motor activity and increase exploratory time.
Anxiolytic effect indicated by:o Increase in the proportion of time
spent in open arms o Increase in the proportion of entries
into open arms
o Circular tank of 100-150 cm diameter with 20-30 cm wall
o A platform of 9-10 cm hidden 2-3 cm below water level
o Add titanium dioxide susp. to make water opaque.
o Temp : 23˚C.
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Anti – anxiety test(light – dark model)
o Rodents – have exploratory activity
o Animals placed in 2 chambered systems, where they can freely move between a brightly –lit open field and a dark corner.
o After treatment with anxiolytic - show more crossings between the two chambers and more locomotor activity.
o Number of crossings between the light and dark sites is recorded. 11
Methodology o Apparatus - a dark and a light chamber divided by a photocell equipped zone.
o Polypropylene animal cage (44 x 21 x 21 cm) is darkened with black spray over 1/3rd of its surface.
o A partition containing 13cm(l) ,5 cm (h) opening is used for separating the dark one-third of the cage.
o This case rests on an activity monitor which counts total locomotor activity. 12
o An electronic system consisting of 4 sets of photocells across the partition.
o It automatically counts movements
through the partition and records the time spent in the light and dark compartments.
o Animals- treated 30 min before the test with drugs or vehicle given i.p. placed in the cage and observed for 10 min.
o Groups of 6-8 animals used for each dose. 13
Observation o No. Of crossings through the partition between
the light and dark chambers compared with total activity counts during the 10 min.
o Loco motor activity also monitored.
Evaluation:o Anxiolytics like diazepam & buspirone
increase locomotor activity and no. Of crossings.
o Non anxiolytics - not effective in this model. 14
Isolation induced aggression
o Male mice subjected to isolation develop aggressive behavior towards other animals of same sex.
o Compounds tested for their ability to suppress this isolation induced aggression.
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Animal used: Male NMRI strain mice
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Evaluation of results:
o No. of animals with complete suppression of aggressiveness.
o Reaction time noted.
o Graduated scale of inhibition of aggressiveness is established.
o Results of test group animals is compared with the control group results.
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Social Interaction In Rats
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Methodology
Parameters measured : o exploration, sniffing, rearing, social
contacts, sexual behaviour, attack, fighting, biting ,defensive posture, immobility and climbing over the partner.
Evaluation :o Values of treated partners compared
with data from control animals – ANOVA and t - test used.
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o mCPP - [ 1-(3-chlorphenyl) piperazine] a 5HT 1c agonist.
o mCPP induces hypophagia and hypo-locomotion , inhibits social interaction, diminishes exploratory activity in light-dark box test, hyper therimia etc,.
o Antagonism of these symptoms is used for screening of anxiolytic drugs.
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Anticipatory anxiety in mice
• When group housed mice are removed one by one
from their former cage, the last mice always have
a higher body temperature than the 1st one.
• The anticipatory increase in temperature was
prevented by prior administration of diazepam &
buspirone
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Test drug/solvent administered p.o to all the 18 animals. Record the basal temp by removing 1st 3 animals/group after 30 min
Difference in the mean value of last three animals and basal value is calculated Vehicle treated group 1- 1.3˚C
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Male Sprague Dawley rats (200- 250g) are housed in groups of 6; exposed to 12 hour light/dark cycle with free access to food and water.
mCPP Induced Anxiety -Locomotion Study
• Test compound or vehicle are administered orally 1h or i.p 30 min before the locomotion test.
• mCPP is injected i.p. in a dose of 7 mg/kg 20 min before the test.
• The animals are placed individually in an automated locomotor activity cages and locomotion is recorded for 10 min.
• Anxiolytic effect : disinhibition of locomotion.25
Parameters measured : o time spent in both sides
(horizontal, vertical activity) o frequency of motion o number of transition
Anxiolytic effect : o increase in parameters measured
in the light/dark box or in number of transitions if test is active.
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Vogel Lick-conflict (Vogel Punished Drinking)
Source of anxiety: thirsty, native rats are
administered shocks while licking water.
Animals used: Sprague dawley rats.
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Apparatus
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Clear Plexiglas box (38 x 38 cm) has a steel grid floor. A water bottle with metal drinking tube at 3 cm above the
grid. A circuit is connected b/w the drinking tube and steel
floor, so that the circuit completes if animal licks the tube.
Methodology
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Parameters measured:o number of accepted punishments
(electric shock)
Anxiolytic effect :o statistically significant increase
in the accepted shocks.
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Staircase apparatus
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