This document discusses models for screening drugs to treat COPD. It describes two in vivo models using anesthetized guinea pigs: 1) the Konzett-Rossler method which measures excess air volume after inducing bronchospasm with agents like acetylcholine to evaluate bronchodilator effects, and 2) measuring spasmolytic activity by inducing spasms with histamine or calcium ionophores in isolated lung strips. Several spasmogens and standard reference compounds are listed. Results are expressed as percent inhibition of induced bronchospasm compared to controls to determine a drug's ED50 value.

1. COPD
BY
JYOTHSNA RAVILLA, M.PHARM (PHARMACOLOGY)
SCREENING MODELS IN

2. COPD(Chronic
Obstructive Pulmonary
Disease)
Accelerated rate of age related lung function decline( structural
changes in mucous lung)
• mucous gland enlargement, epithelial thickening, mucous hyper
secretion and occlusion by inflammatory mucous exudates.

3. TREATMENT:
• Long acting Bronchodilators: β agonists(salmeterol),
anticholinergics(ipratropium), corticosteroids(prednisone).
• for successful preclinical screening and to know the effectiveness of
the drug we should first induce opposite conditions in animals.

4. TYPES OF MODELS
• Invitro: histamine receptor binding
• effects on airways:
1. Tests on isolated organs.
2. in-vivo
• Anti- tussive activity
• effects on tracheal cells, bronchial mucous secretion and transport.

5. IN-VIV0 TESTS:
• Broncho spasmolytic activity in anesthetized guinea pig (KONZETT-
ROSSLER method)
• Effect of arachidonic acid or PAF on respiratory function.
• Bronchial hyperreactivity
• Body plethysmography and respiratory parameters after histamine induced
bronchoconstriction in anaesthetized guinea pig.
• Pneumotachograph in anaesthetized guinea pigs.
• Airway microvascular leakage.
• Isolated larynx in situ

6. 1.Broncho spasmolytic activity in anaesthetized
guinea pig (KONZETT-ROSSLER METHOD)
• Purpose and rationale:
The method is based on registration of volume changes of a living
animal in a closed system consisting of a respiration pump, of the
trachea and the bronchi as well as of reservoir permitting
measurement of volume or pressure of excess air.
The method permits the evaluation of a drug’s bronchospasmolytic
effect by measuring the volume of air, which is not taken up by lungs
after bronchospasm.
The degree of bronchospasm can be quantified by recording the
volume of excess air.

7. Procedure:
Animal: guinea pig(m/f) weight: 250-500g
Method:
1. animal should be anesthetized with i.p. urethane.
2. anaesthesia should be deep enough to prevent the spontaneous
respiration.
3. trachea cannulated by two way cannula: one arm connected to
respiratory pump, other to Statham P23 transducer.
4. Animal artificially respired using starling pump with inspiratory pressure
set at 90-120mm of water, tidal volume: 3ml/100g body weight,
frequency: 60 strokes/min.
5. Excess air, not taken up by the lungs measured and recorded on
polygraph.
6. Internal jugular vein cannulated- admins of spasmogens and test
compound.
7. Carotid artery cannulated to measure BP.

8. TESTING:
Spamogens (i.v.)
1. Acetylcholine hydrochloride (20-40 μg/kg), or
2. methacholine (20-40 μg/kg) or
3. histamine dihydrochloride (5-20μg/kg) or
4. Bradykinin triacetate (10-20 μg/kg) or
5. ovalbumin (1mg/kg), or
6. PAF (25-50 ng/ml) or
7. leukotrienes LTC4, LTD4 (about 1μg/kg) or
8. Substance P (0.5 μg/kg)
After two bronchospasms of equal intensity- test drug is given
i.v/i.m/p.o/s.c or intraduodenally.

9. 9. Spasmogen given again 5, 15 and 30 mins after i.v administration of
the drug.
10. 15, 30 and 60 min after intraduodenal administration of drug.
11. 30 and 60 mins after p.o. administration of the drug.
STANDARD COMPOUNDS USED:
• Atropine sulphate(0.01 mg/kg, i.v.) to inhibit acetylcholine or
methacholine induced spasms.
• Aminophylline (6 mg/kg, i.v.) to inhibit bradykinin induced spasms.
• Tolpropamine-HCL (0.2 mg/kg) to inhibit histamine induced spasms.
• Imipramine- HCL (3-5 mg/kg) to inhibit serotonin creatinine induced
spasms.

10. EVALUATION:
• Results are expressed as percent inhibition of induced bronchospasm
over the control agonistic responses.
• The ED50 value is calculated.

11. 2.Spasmolytic activity in isolated guinea pig
lung strips.
• Purpose and rationale: to check the spasmolytic activity induced by
histamine and calcium ionophores.
PROCEDURE:
Animal: albino guinea pigs sex: m/f weight: 300-450g
Method: sacrificed either by ether overdoses. Lungs isolated. Cut into strips
of 5cm in PSS. Mounted in organ bath. Bubbled with carbogen, maintained
at room temperature. Tissue left to equilibrate for 30-60 mins.
• prior to testing carbachol added to check their ability to contract.
• 20mins later, two pre values are obtained by adding the spasmogen and
record the contractile force at maximum level.
• 20 mins eq. period -spasmogen again given 5 mins later- test compound
added in cumulative doses at 5-10 mins interval. Contractile response
determined.

12. • histamine dihydrochloride 10-6 g/ml for 5min or
• Ca –ionophore 5x 10-6 g/ml for 5min or
• leukotriene LTC4 10-9-10-8 g/ml for 10min or
• leukotriene LTD4 10-9-10-8 g/ml for 10 min
EVALUATION:
%inhibition of spasmogen induced contraction is calculated.