2. Introduction
Herbal drugs having there major action on
cardiovascular disorders are designated as
cardiovascular drugs.
They can act directly on cardiovascular structure or
through central nervous system, kidney, hormones
which regulates cardiovascular function.
Screening of this drugs for there activity became
important for there use in human subject.
Mainly animal studies are carried out for this
purpose
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3. Following are the major cardiovascular
disorders
Arrhythmia
Angina
Hypertension
Congestive heart failure
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4. Screening of antiarrhythmic drugs
The screening of anti-arrhythmic is done by
two different methods.
• In-vitro models
1. Lagendroff technique:
• In-vivo models :
Chemically induced arrhythmia
Electrically induced arrhythmia
Exercise induced ventricular fibrillation
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5. In-vitro models
Lagendroff technique:
Principle :-
-force of contraction, heart
rate, Incidence and duration of ventricular
fibrillation or ventricular tachycardia is
recorded in the control as well as test
group using this Principle this technique is
carried out.
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6. Animal – selected
Sacrificed (stunning)
heart – removed – placed in Ringer’s solution (37⁰C)
Aorta – located and cut – cannulated with Ringer’s solution
(perfused at 40 mm Hg)
Ligature – placed around LAD
Test /std/control - administered.
Occluded for 10 minutes
reperfusion
ECG electrode – pulsatile stimulation, induction of arrhythmia
Heart rate and contractile force –measured
Procedure:
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8. EVALUATION:
Heart rate
Contractile force (force transducer)
Incidence and duration of ventricular
fibrillation or ventricular tachycardia is
recorded in the control as well as test group
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10. Chemically induced arrhythmia
A large number of agents are capable of
inducing arrhythmias.
e.g. anesthetics like chloroform, ether,
followed by a precipitating stimulus such as
adrenaline, some alkaloids cause arrhythmia.
Principle :- Aconitine acts persistently on
sodium channels and activates them causes
ventricular arrhythmias using this study is
carried out
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11. procedure
Animals [Male rats (300-400g)]
Anesthetized
Test / std/control – administered
↓
Aconitine (5μg/kg +0.1N HNO₃) (administered
through saphenous vein)
↓
ECG – Recorded (lead II)
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12. observation
Anti-arrhythmic effect of test is measured by
the amount of Aconitine/100g animal.
Includes:
Ventricular extra systoles
Ventricular tachycardia
Ventricular fibrillation
Death
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14. EXERCISE INDUCED
VENTRICULAR FIBRILLATION
Principle
Tests combining
coronary constriction
with physical
exercise may
resemble most
closely the situation
in coronary patients
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15. production of MI
↓
Animals – run on a motor –driven treadmill
↓
Work load - ↑every 3 min for total of 18 min
↓
During last minute-treadmill is stopped- left
circum flex artery- occluded for 2 min
↓
After 10-20 sec of VF – defibrillation is achieved
without any delay by placing large metal plates
across animal’s chest.
observation
HR is measured
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16. Screening of anti-anginal drugs
In Vitro Models
Isolated heart (Langendorff) technique.
In Vivo models
Myocardial ischemic preconditioning model
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17. Ischemia preconditioning model
Principle: Preconditioning(brief duration of ischemia
and reperfusion) can reduce damage produced by
prolonged ischemia and reperfusion
Rabbits are anaesthetized with ketamine
Artificial respiration is established and vessels
cannulated
4- suture is looped around marginal branch of LCA
.Loop is tighten for 5 min, loosened for 10 min
Test drug administered
Tighten for 30 min followed by 120 min of
reperfusion
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18. observation
The animals are sacrificed after the
reperfusion duration.
Comparisons between systemic
hemodynamic data and infarct size studies
are analyzed by ANOVA using statistical
software.
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19. Screening of Antihypertension drugs
IN VIVO MODELS
ACE Inhibition in rat
Tail cuff method
IN VITRO
Monocrotaline Induced Pulmonary Hypertension
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20. ACE INHIBITION IN RAT
Principle:
Angiotensin –I is converted to
angiotensin II by ACE which causes increase
in blood pressure using this test drug are
tested.
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21. Male Sprague- Dawley rats (200-225gm) are
selected..
They are anaesthetized with 60mg/kg of
phenobarbitone sodium i.v.
The right artery is cannulated for recording the
pressure.
The jujular vein is cannulated for i.v. test
injection.
The B.P is diminished by the administration of
5mg/kg of pentolinium i.p.
Now Ang I is injected i.v. saline.
The injection is repeated in 5min interval until
an identical pressure is attained.
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22. The test drug is administered at a dose of
10mg/kg intravenously or 25mg/kg
intradeudenally.
Again Ang I is injected as the similar dose
above.
The diminution of the pressure after the
administration of potent ACE inhibitors is
compared .
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23. TAIL CUFF METHOD
Widely used to evaluate the antihypertensive drugs in
experimentally induced animals.
Charles River male rats(300-350g) are anaesthetized
using I.P injection of 0.8ml of 4% of chloral hydrate.
Both the kidneys are exposed, hypertension is induced by
placing a silver clip on both renal arteries.(0.2mm dm &
4mm l)
After 5 to 6 weeks operated animals attain renal
hypertension with systolic B.P of 170 to 200mmHg.
A tubular inflatable cuff is placed around the base of tail
and a Pizo- electric pulse detector is positioned distal to
the cuff.
The cuff is inflated to approximately 300mmHg.
As the pressure in the cuff is released slowly, the systolic
pressure is detected and recorded in the poly graph.
Test substance is administered intra peritonially for
alternative days in three times.
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25. IN VITRO MODELS
MONOCROTALINE INDUCED
HYPERTENSION
MONOCROTALINE, a pyrrolizidine alkaloids
derived from Crotaloria spectabillis.
Sprague- Dawley rats (200-225gm) of either sex
are selected.
Animals are fed with test drug for one week prior
to S.C injection of MONOCROTALINE
100mg/kg.
Animals are sacrificed 7 or 14 days later and their
hearts and lungs are excised.
Left ventricle and lung are weighed, along with
main, extra and intrapulmonary, artery are
isolated.
After 1hr arteries are made to contract with KCl.
Contractions are recorded using lever transducer.
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26. Maximum force generated by an artery is
plotted as a function of applied force and
recorded on a polygraph.
Contraction and relaxation of agonist
responses of artery are assessed.
Cumulative Conc. response of KCl,
Angiotension II, and NOR-Epinephrine are
plotted.
Both the responses are plotted as a function
of negative log of agonist Conc.
To compare the differences in mean
responses, t-test is applied.
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27. Cadiotonic drugs
Isolated heart technique
Animal :-guinea pig
Principle:-force of contraction and
coronary flow measurement s carried out
to fin out activity of cardiotonic drug.
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28. Procedure:
operate and expose heart of animal
cannulate inferior vena cava
perfuse with ringer solution
arrange the organ bath
test drug administration
record result on kymograph
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29. Observation
Calculate heart rate and contraction
amplitude
A positive chronotropic effect from dose
response curve shows cardiotonic activity.
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30. References
H. Gerhard Vogel (Ed.)Drug Discovery and
Evaluation:Pharmacological Assays,springer
publication
Dr. S.L. Deore, Dr. S.S. Khadabadi, Dr. B.A.
Baviskar, Pharmacognocy & Phytochemistery,
A comprehensive approach pharma med press.
Kd tripathi essintials of medical pharmacology
seventh edition jaypee publiction
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