To study the effect of drugs on perfused frog heart.

This is a experiment-2 of pharmacology-2, B.Pharmacy, 3rd year.

Aim

To study the effect of drugs (inotropic and chronotropic actions) on perfused frog heart.

Reference
S.k Kulkarni, A textbook of experimental pharmacology, Vallabh Prakashan, page no- 196-197.

Requirements

Animal– Frog

Drugs

• Adrenaline (stock solution 10 µg/ml)
• Noradrenaline (stock solution 10 µg/ml)
• Acetylcholine (stock solution 10 µg/ml)
• Calcium chloride (stock solution 10 mg/ml)
• Potassium chloride (stock solution 10 mg/ml)

Physiological solution Frog Ringer So IAEC As indicated under.

Equipment– Frog board, thread, Surgical instruments, universal heart lever.

Principle

Drugs may influence the rate (chronotropic) and force (inotropy) of heart contraction. An increase in the heart rate is called a ‘positive chronotropic’ response, and a decrease in heart rate is called a ‘negative chronotropic’ response. Similarly, an increase in the force of contraction is called a ‘positive inotropic response, and a decrease in the force of contraction is called a ‘negative inotropic response. Sympathomimetic amines such as adrenaline and noradrenaline produce a positive inotropic and a positive chronotropic response. In other words, adrenaline increases both the heart rate (tachycardia) and the force of contraction of the heart muscle. Whereas parasympathomimetics such as acetylcholine produce negative inotropic and negative chronotropic responses.

Procedure

1. Pith the frog and pin it to the frog board.
2. Give a midline incision on the abdomen. Remove the pectoral and expose the heart.
3. Carefully remove the pericardium and put a few drops of frog Ringer over the heart.
4. Trace the inferior vena cava, put a thread around it ad give a cut to insert the venous which is connected to a perfusion bottle containing frog Ringer. Insert the cannula in the vein and tie the thread to ensure the cannula is in place.
5. Give a small cut in one of the aortae for the perfusate.
6. Adjust a proper venous pressure of 2-4 cm by altering the height of the perfusion bottle. The effective venous pressure is the height in cm from the level of the venous cannula and the Ringer level in the perfusion bottle. The use of Marriott’s bottle helps in attaining constant pressure. Start the perfusion by opening the screw clamp attached to the tube.
7. Pass a thin pin hook through the tip of the ventricle, and with the help of a fine thread attached to the hook, tie it to the free limb of the universal lever, which is fixed to a stand. Adjust proper tension and magnification by altering the height of the lever. Record the normal contraction of the heart on the smoked drum.
8. Inject 0.1, 0.2, 0.5, and 1 ml of the stock solution of each drug in sequential order and note the change in the rate and amplitude of contraction. Keep at least 5 min gap between the administration of each dose of the drug. The drug is administered by injecting the drug into the perfusion tube very close to the venous cannula. Take precautions to avoid any leakage of the drug from the tube, and the injection of air bubbles.
9. Label and fix the tracing with the fixing solution.

Result

The effect of drugs (inotropic and chronotropic actions) on perfused frog heart was studied.

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