Effect of histamine on isolated tracheal preparations

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BACKGROUND

Guinea pigs are the commonly employed animal species for the study of effect of drugs on isolated tracheal muscle preparations.¹ Histamine is a chemical transmitter released by mast cells and basophils shows a significant effect on bronchial air ways. On bronchial smooth muscles it causes constriction that may be responsible to bronchial hypersensitivity, a common characteristic of asthma.² The aim of the present study is to evaluate the effect of histamine on isolated trachea of guinea pig.

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REQUIREMENTS

Animals required: Guinea pigs weighing 250-300 gms

Drugs: Histamine 30 µg/ml

Reagents used: Kreb’s solution

Instruments used: Dissection apparatus, Organ bath assembly, Kymograph, Aeration tube cum tissue holder, Haemostatic forceps, and frontal writing lever.

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PROCEDURE

Select the guinea pig and sacrifice by cervical decapitation. Isolate the trachea carefully and prepare individual tracheal rings of size 2 mm from lower third of trachea by using scissors and place them in an organ bath. Tie over 5-6 rings carefully by using silk thread to form a chain. Then suspend the tracheal chain in an organ bath containing Krebs solution. Maintain the temperature of the bath at 37±0.5ºC and aerate it continuously. Attach one end of the tracheal chain to S-shaped aerator tube and the other end to isotonic frontal writing lever placed over smoked drum. Stabilise the tracheal preparation in the bath for about 30-45 minutes under a load of 400 g. Then inject different doses of histamine in geometric progression (0.1 ml, 0.2 ml, 0.4 ml, 0.8 ml, 1.6 ml and 3.2 ml). For each dose, the drum has to run for about 90 seconds. After that, wash the tissue with Kreb’s solution for 2-3 times. For each washing, at least a time gap of 2-3 minutes is to be maintained. From the responses obtained, plot a graph directly on a semi-log paper on X-axis. Measure the responses for each dose and the percentages of the maximum response are to be plotted along the Y-axis against corresponding doses.³

Determine the dose histamine which produces 50% response. Convert the response to its molar concentration.

Calculation of pD2 value of histamine

Determination of the concentration of histamine in the organ tube which produce 50% response

Y= (Quantity to produce 50% response (X) × Conc. of histamine used)/(bath capacity (mL))

Calculation of EC₅₀

Mol. Wt. of histamine=

Calculation of pD2

pD2= -log 10[EC50]

OBSERVATION

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CONCLUSION

pD2 value of histamine is ……..

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REFERENCES

1. Castillo JC,  De Beer EJ. The Tracheal Chain I: A Preparation for the study of antispasmodics with particular reference to bronchodilator drugs. J Pharmacol Experimental Therapeutics. 1947;90(2):104-9.
2. Gvozden Rosic, Zorica Lazic, Suzana Pantovic, Mirko Rosic. Phenylethylamine Effects On Histamine-Induced Contraction Of Isolated Guinea-Pig Trachea Rings. Jugoslov Med Biohem. 2005;24:95–7.
   
3. Jawale NM, Shewale AB, Nerkar GS, Patil VR. Evalution Of Astihistamitic Activity Of Leaves of Piper Betel Linn. Pharmacologyonline. 2009;3:966-77.