Screening of Anti Parkinson's Disease Agents

8/11/2019 Screening of Anti Parkinson's Disease Agents

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By,

Dr. Manoj Upadhya,

SKBCOP, Kamptee


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It is a degenerative disorder of Central Nervous System

Extensive degradation of dopaminergic neurons of the

Substantia nigra.

oGenetic

oEnvironmental triggers

oExcitotoxicity (excess Glutamate)oOxidative stress


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Akinesia: Difficulty in

initiating movement

Bradykinesia: Slowness of

movement

Rigidity: Muscular stiffness

Tremors: Shaking

movements of periphery


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Muscarnic agonsits(Tremorine and Oxotremorine)

Tremor, Ataxia, Spasticity, Salivation,

Lacrimation, Hypothermia

Anticholinergic drugs


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Test compound or standard

(5 mg/kg benzatropine mesilate p.o.) is administered(1 h)

Oxotremorine (0.5 mg/kg s.c.)

Rectal temperature is measured before administration and

1, 2 and 3 h after oxotremorine

is scored after oxotremorine administration for 10sec after every 15 min for 1 h,

are scored 15min and 30min after oxotremorine inj.Scoring scale

Tremor, Lacrimation or Salivation Score

Absent 0

Slight 1

Medium 2

Severe 3

Procedure:Mice 18-22 g
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EvaluationHypothermia

The average values are compared statistically with the control group

TremorThe total score is summarized. The number in the treated group are

expressed as percentage of number of control group

Salivation and Lacrimation

The total score is summarized. The number in the treated group are

expressed as percentage of number of control group

The oxotremorine antagonism has been proven to be a

reliable method for testing central anticholinergic

activity.

The overt isomorphism between the animal model and

the symptoms of Parkinsons disease recommend this

test for screening of anti-Parkinson drugs.


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N-MPTP (N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine)

Partial destruction of basal ganglia

Syndrome that resembles Parkinsons disease(Akinesia, rigidity, postural tremor, fixed posture, eyelid

closure, drooling)

Scoring of severity is done trained observer on the

scale of 0 (normal) to 17 (max severity) .

Evaluation


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Reserpine induces depletion of central catecholamine stores.

Sedative effect followed by signs ofeyelid ptosis, hypokinesia, rigidity, catatonia, and immobility

Dopamine agonists


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Procedure:

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Mice 20-25 g

Reserpine (5 mg/kg i.p.) is administered

(24 h)

Test drug or standard

Signs are observed in Perspex container (30 x 26 cm, 20 cm high)

Horizontal movements are recorded for 10 min

Raring and grooming episodes are registered by an experienced observer.

(30 min)

Evaluation

Locomotor activity and grooming scores of treated animals

are compared with control and vehicle treated animals.


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Unilateral lesions of dopaminargic nigrostriatal pathway by

neurotoxin 6-hydroxydopamine (6-OHDA)

Hypersensitivity of postsynaptic dopaminargic receptors in

striatum of lesioned side.

The rat rotates ipsilateral when indirect acting compound like

amphetamine is administered.While rotates contralateral when direct acting dopamine

agonist like apomorphine or dopamine precursor L-dopa is

given.


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Procedure: W. Rats 200-250 g

Rat skull fixed in stereotaxic frame

Coordinates positioned according to atlas

2mm diameter hole is drilled by using electrical drill(Care not to damage the meninges)

(Anasthesia)

30 gauge stainless-steel cannula is aimed at anterior zona compacta of substantia nigra

8 g of 6-OHDA in 4 L of saline is injected at the rate of 1 L/min

Wound is closed and animal is allowed to recover for several weeks


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Evaluation

Percent change of drug turns from control turns is

recorded.


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Elevated body swing test as a measure ofasymmetrical motor behavior of hemiparkinsonian

animals in drug free state


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Procedure: W. Rats 200-250 g

Rat skull fixed in steriostaxic frame

Coordinates positioned for substansia nigra according to atlas

2mm diameter hole is drilled by using electrical drill(Care, not to damage the meninges)

(Anasthesia)

30 gauge stainless-steel cannula is aimed at left substantia nigra

8 g of 6-OHDA in 4 L of saline containing 0.02 % ascorbic acid is injected at the rate of

1 L/min and needle is left for more 5 min before retraction

Wound is closed and animal is allowed to recover for one week


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Rat is rested on floor with all 4 pows on the ground

Rat is held above 2.5 cm from the base of its tail and elevated 2.5 cm above the surface on

which it is being rested

A swing is recorded when animal moves its head out of the vertical axis to either side

Swings are counted for 60s in 15s segments

Swings to each side (ipsilateral or contralateral) are counted and rcorded as percentage of total

swings

TWO way ANOVA is used to analyze swing behavior data across the 15s segments


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Paxinos, G., and Watson, C. The Rat Brain in

Stereotaxic. Coordinates, 6th ed. Elsevier/Academic

Press, New York, 2007

Vogel H G, Drug Discovery and Evaluation, Pharmacological

Assays, Springer-Verlag Berlin Heidelberg 2002

Documents

Screening of Anti Parkinson's Disease Agents