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PRECLINICAL STUDY OF ANTI -PARKINSONIAN DRUGS

Presented by: SANDIP CHAUDHARIM. PHARM (1St SEM)

Department of Pharmacology

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Contents

Introduction

Etiology Pathophysiology Classification Mechanism of action

In vivo preclinical evaluation

In vitro preclinical evaluation

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Introduction (Rang & Dale,2002, Richard ,A.H. 2000)

Parkinson's disease (PD) is a neurodegenerative movement disorder characterised by progressive loss of dopaminergic neuron in substantia nigra and depletion of the neurotransmitter Dopamine in the striatum. image

Features Hypokinetic movement Akinetic- Difficulty in initiating movements & decreased

spontaneous movements. Bradykinesia – Slowness of movement.

Decreased associated movements- Expressionless face or mask face.

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Hyperkinetic movements Rigidity – The limbs offer resistance to passive bending

throughout the movement. Tremor – Observed only at rest. Festinant gait- Trying to catch the center of gravity.

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Famous Faces of Parkinson

Michael J. Fox Muhammad Ali Katharine Hepburn

Pope John Paul II Johnny CashMao Tse Tung

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Etiology(Tripathi,2004)

Idiopathic Drugs MPTP Genetic

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Pathophysiology (Goodmann & Gilmann,1996)

DA

ACH

PD due to DA

PD due to ACH

Levodopa Inhibitory

ExcitatoryCentral anti cholinergics drugs

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(Frongois, W. et.al. 2003)

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Classification: (Tripathi K.D,2004)

Dopamine analogues: Levodopa

Peripheral deoxy decarboxylase inhibitor: Carbidopa, benserazide

COMT- inhibitors: Tolcapone, Entacapone

MAO-B inhibitors: Selegiline, Clorgyline

Dopamine agonists: Rosipirole , Pergolide

Central anti- cholinergics: Benzotropine ,biperiden

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IN VIVO MODEL MPTP model in animals

A. MPTP model in mice

B. MPTP model in monkey

Circling behavior test

Elevation body swing test

Reserpine antagonism

Tremorine & Oxatremorine antagonism

Specific test for evaluating locomotor activity

A. Skilled paw reaching test

B. Stepping test C. Gait Analysis12

Principle: MPTP acts as- a neurotoxin which preferentially affected

dopaminergic cells in substantia nigra par compacta .

MPTP shows toxicity due to conversion into MPP+ by MAO enzyme.

This ion acts by inhibiting the ET system of mitochondrial complex -1.

Most popular MPTP model : 1. MPTP model in mice. 2.MPTP model in monkey.

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MPTP Model in animal (Von Bohlen,2006)

MPTP model in monkey s(Vogel, H .G. et al 2002)

Principle:

N-MPTP

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Partial damage to basal ganglia

PD like symptom

DA precursor L-dopa

Reversed

leads to

i.v.

Requirements :

Animal - Rhesus monkey (5-8 kg).

Drug - N-MPTP up to 10-18 mg/kg i.v. for 5-8 days. Test drug

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Procedure:

Take 8 rhesus monkey (5-8 kg) of either sex

Administered the N-MPTP i.v. with cumulative dose up to 10-18 mg/kg for 5-8 days.

Produces PD like symptoms

Administered test drug

Symptoms are Evaluated

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Evaluation :

The severity is rated by using scale of 0 (normal ) to 17 (max)

Observation Scoring(1) Movement Normal Reduced Sleepy

01 2

(2) Checking movement Present Reduced Absent

01

2

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Observation Scoring(3) Attention& blinking Normal Abnormal

0 1

(4) Balance & co-ordination Normal Impaired Unstable Falls

0 1 2 3

(5) Vocalization Normal Reduced Absent

0 1 2

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MPTP model in mice (Wei, Zhang, et.al,2004)

Principle:

Neuro protective effect of test drug measured in MPTP model in mice.

SN area is especially rich in microglia activation release a variety of neurotoxic factors like superoxide, NO, cytokines & eicosanoids.

Test drug reduces NADPH oxidase activity at extracellular & intracellular level.

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Requirements:

Animal - mice-wild strain (C57BL/6J). mice-null strain.

Drug - MPTP (15mg free base/kg) s.c. & test drug

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Procedure:

Take NADPH - Oxidase null & wild type mice

MPTP (15mg/kg) injected s.c. to mice daily for

6-consecutive days

Then test druginjected to mice twice daily for

first 6-days& then inject once daily for remainder study

After 6-days of last MPTP injection, mice are killed

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Striatal tissue are rapidly dissected

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Striatal cell viabilityestimation

NO release estimate by assays

ROS estimate byFluorescence assays

Evaluation: Test drug evaluated for showing neuro protective action .

Reducing NADPH Oxidase activity in PHOX+/+ (wild strain)

is present but in PHOX-/-, NADPH Oxidase are absent .

Reduces MPTP induced production of superoxide free

radicals extracellular level& intracellular ROS.

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Circling Behavior in rats (Bracha, H.S., et.al, 1986)

Principle :

An imbalance of dopaminergic activity within the basal

ganglia is associated with markedly asymmetric

circling behavior (Rotation turning) which measured by

Rota meter.

This model is used in drug induced rotating behavior

and understanding of extra pyramidal disorder & of

their treatment by dopaminergic agents.24

Requirements:

Animal - Sprague-Dawely rats(150-175gm)

Dose - 6-OHDA(8µg in 4µl of 0.2mg/ml ascorbic acid in saline ) & test drug

Apparatus – Rotameter

(www. harvardapparatus.com)

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Procedure: Female Sprague Drawley rats are taken Rats are anesthetized with Pentobarbital

(60mg/kg)

Head is placed in stereotaxic device (www.supertech.com)

Stereotaxically lesioned in left substantia nigra (www.jove.com)

6-OHDA are injected into left SNr of rats

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L-desipramine.HCl (25mg/kg) are injected 30 min.

prior to 6-OHDA injected.

Rats are divided into groups:

Control groups for base value of ipsilateral rotation -

2.5mg/kg of d-amphetamine injected i.p. to rats.

Control groups for base value of contra lateral

rotation- 1mg/kg of Apomorphine injected i.p. to

rats.

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Further studied test group as compared to control group.

No. of full turns( either ipsilateral Or contra lateral turning to

lesion) are recorded an automatic print out counter every 15

min. for one or two hr. session.

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Observation :-For ipsi-lateral turning :

- administer 2.5 mg/kg Amphetamine &placed in circling chamber for 2 hour

For contra-lateral turning :- administer 1mg/kg & placed in

circling chamber for 1hour

Test compound are given i.p. or s.c. & record reading with 15 min. interval.

Evaluation :-% change of drug turns from control turns is recorded.

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Elevation body swing test (Cesanov, B;1995)

Principle:

EBST measures asymmetrical motor behavior of hemiparkinsonian animals in a drug free state & drug induced state.

Drug induced motor behavior widely used as-behavioral index of hemi parkinsonian animals.

High positive co-relations b/w swing & Apomorphine induced rotational behavior.

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Requirements:

Animal - Sprague Dawley rats

Drug - 6-OHDA (8 mg in 4ml 0.9% saline containing

0.02% ascorbic acid).

Test drug

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Procedure: 40 rats are taken as test group Anesthetised with sod. Pentobarbital(60mg/kg i.p.) mounted in stereotaxic device

stereotaxically lesioned in left substantia nigra

6-OHDA solution are injected over 4min. & needle left in place for an additional 5 min. before retraction.

7 days after lesion, behavioral testing is performed .

Remaining 24 animal served as-control group. The animals are placed into a plexiglass box (40x40x35.5 cm.)

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Sr. no. 15 sec 30 sec 45 sec 60 secLS RS LS RS LS RS LS RS

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Observation : A swing is recorded whenever the animal moves its head out

of vertical axis. swing are counted for 60 sec. with interval of 15sec.

Evaluation:-

Σno. of swing towards left side % left swing = Σ L+R

Σno. of swing towards right side % right swing = Σ L+R

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Reserpine antagonism (Salvador, H.L., et al, 1996)

Principle:

The ability of anti-cholinergic agents microinjected in subthalamic nucleus to reduce Reserpine induce muscular rigidity are assesed in rats.

Electro myographical activity of gastrocnemiussoleus muscle are used as- a parameter of muscular rigidity.

Reserpine increases high cholinergic tone in subthalamic nucleus result in increased muscular rigidity.

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Requirements:

Animal : male rats (Wistar strain 280-300 gm)

Drug – Chloral hydrate (350mg/kg i.p.)

Reserpine (5mg/kg i.p.)

Apparatus- photocell

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Procedure: male rats are taken

reserpine (5mg/kg i.p.) injected to rats

30min. Prior to observation test compound is injected

animals are placed singly on to floor of Perspex container (30x26x20 cm.) which situated on panlab proximally sensor unit.

Horizontal movement are recorded for 10min.

rearing & grooming episodes are registered

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Evaluation :-

Locomotors activity & grooming scores of test group is

compared with control group.

Tremorine & Oxotremorine Antagonism (Parmar N.S,2000)

Principle:

Tremorine and Oxotremorine is a muscarinic receptor agonist, producing imbalance between the level of Ach & DA, so inducing a parkinsonism. Produces a sign like tremors, ataxia, salivation, lacrimation & hypothermia.

The signs are antagonized by test drug.

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Requirements

Animal- NMRI mice ( male) (18-22gm) Group- 2, each contain 6-10 mice

Drug- Test/ std , & tremorine or oxotremorine

Dose- 5 mg/kg of standard drug 0.5 mg/kg oxotremorine

Route- s.c. for oxotremorine

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Procedure-

6-10mice are taken

0.5mg/kg Oxotremorine s.c administered

After 1hr test drug were given orally

Tremor is scored after Oxotremorine dosage in 10 sec. observation

periods in every 15 min.

Salivation & Lacrimation are scored 15 & 30 min.

after Oxotremorine injection.

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SCORING:-

Tremors/ lacrimation Scoreabsent 0slight 1medium 2severe 3

video

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Evaluation :-

1) Hyperthermia :-Average value of temp. in both group – comparedstatistically.

2) Tremor :-The score for all animals in each group. at the 3observation periods are summarized . The numbers in the treated groups. are expressed as% of the no. of the controlled group.

3) Salivation & lacrimation :-The course for both groups. are summarized at the 2observation periods & expressed as % of the no. of control group.

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Skilled paw reaching test (Tracy, D.F., et.al., 2002)

Principle:

This method used to evaluate symptoms and treatment in rat by skilled reaching with fore paw for food.

Unilateral DA depletion reduces success by abnormalities in movements including changing in posture, shortened reaches and loss of pronation and spuniation.

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Requirements:-

Animal - long Evans rats (250-310gm)

Dose - Des methyl Imipramine (25 mg/kg i.p.)

6-OHDA (2μl of 4mg/ml in 0.95% saline with

0.02% ascorbic acid)

Equipment- Single pellet boxes (25x35x30cm)

Food tray boxes(10x18x10cm)

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Procedure:-

20 rats are taken

30minute before surgery, desmethylimipramine administered

(25mg/kg i.p.)

Rats anesthetized with pentabarbital(60mg/kg i.p.)

12 rats received 6-OHDA lesions but 8 rats not received

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Scoring reaching success:-

Reaching performance are scored by counting misses and

successful reaches for each limb.

1. Scored as “reach”.

2. Scored as “hit”.

Success% = no. of reaches /no. of hit x100

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Reaching posture

• Two point scale

• Scored as 0

• Scored as 1

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Stepping Test in Rats (Olsson M. et. al,1995)

Principle:- This model is clinically relevant to unilateral model

for parkinsonism akinesia. The 6-OHDA lesion induced marked and long-

lasting impairments in the initiation of stepping movements with the contra lateral paw which can be ameliorated by application of drug.

Requirement:- Animal: Sprague Drawley rats Dose: 6-OHDA (3.6μg/μl in 0.2 μg/ml Ascorbate saline) test drug

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Procedure:- Rats were placed in a steriotaxic device 6-OHDA injected into the right ascending mesostriatal Experimental setup for stepping test.

Evaluation parameter:-Initiation time, Stepping Time, Step length.

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Step length = Length of ramp / no. of steps

Sequence of testing in right paw & followed by left paw

testing, repeated twice.

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Gait analysis (Nancy ,J.S. 2006)

(Jeffrey M. Hausdorff, et al. 1998)

Gait analysis is useful in objective assessment of

walking ability and identify causes for walking

abnormality in parkinsonism disease.

The result of gait analysis is useful in determining best

course of treatment.

Catwalk method is mostly used to analyze gait in lab.

Animal.

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Catwalk parameters- Regularity index Phase – lag Phase – lag variability Phase – lag mismatch %

Symmetrical gaits are divided into two groups- A. Lateral sequence ( LS) gaits B. Diagonal sequence(DS)gaits

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Rotenone induced parkinsonism (Todd, b., et.al.,2002)

Principle:-

Chronic systemic complex 1st inhibition caused

by Rotenone exposure induces of parkinsonism in rats

including selective nigrostriatal dopanimergic

degeneration & formation of ubiquitin & α-synuclein

inclusion .

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Materials & Method:-

Cell culture – SK-N-MC neuroblastoma cell

Culture medium –minimum essential medium

Reagents –rotenone(5nm) prim. Abs & sec. Abs

Visualizing reagent -3,3-diaminobenzidine

Apparatus – bright field microscope

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Procedure :

SK –N- MC neuroblastoma cells cultured in MEC medium containing rotenone

cells are incubated in prim. Abs for 24 hr.& followed by sec. Abs for 1hr

Added visualizing agent

Observed under bright field microscope.

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Evaluation :

After 4 weeks, chronic rotenone exposure leads to –

Synuclein & Ubiquitin level increased

Reduced glutathione level.

Caused oxidative protein damage.

Caused oxidative DNA damage.

Increased apoptotic death.

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THANK YOU

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