References
1. Guyton, A.C., & Hall, J.E. (2016). Textbook of Medical Physiology (13th ed.). Elsevier.
2. Berne, R.M., & Levy, M.N. (2001). Physiology (5th ed.). Mosby.
3. Evans, H.M., & Norris, H.E. (1917). The effects of drugs on the isolated frog heart. Journal of Pharmacology and Experimental Therapeutics, 12(3), 123-145.
4. Randall, W.C., & Williams, E.A. (1960). Effects of various drugs on the frog heart. American Journal of Physiology, 198(5), 987-992.
Introduction
The isolated frog heart experiment is a classic physiological procedure used to study the effects of various drugs on cardiac function. The frog heart, particularly the Rana temporaria species, provides a valuable model due to its well-preserved cardiac rhythm and easy isolation for in vitro studies. This experiment helps in understanding the pharmacological effects on heart rate, contractility, and rhythm.
Objective
To investigate the effects of different drugs on the rate and force of contraction of the isolated frog heart.
Materials and Equipment
Frog (Rana temporaria), Dissection tools (scissors, forceps, etc.), Ringer’s solution, Experimental drugs (e.g., adrenaline, atropine, digitalis), Physiological recording apparatus (e.g., kymograph or digital recorder), Thermometer, Beakers and pipettes, Stopwatch, Tissue bath
Procedure
1. Preparation of Frog Heart:
Anesthesia and Dissection: Anesthetize the frog using a suitable anesthetic (e.g., MS222). Dissect the frog to isolate the heart carefully.
Heart Removal: Remove the heart and place it immediately in a beaker containing Ringer’s solution to maintain its physiological conditions.
2. Setup: Mount the isolated heart in a tissue bath filled with Ringer’s solution, ensuring it is connected to a recording apparatus.Set up the apparatus to monitor heart rate (beats per minute) and contractility (force of contraction).
3. Control Measurement: Record the baseline heart rate and contractility without adding any drugs. This serves as the control data.
4. Drug Application: Add the first drug to the Ringer’s solution. Wait for a steady state to be reached before recording data.Measure the effects on heart rate and contractility.Repeat the process for each drug being tested. Ensure a washout period between drugs to return the heart to baseline conditions.
5. Data Recording: Record the heart rate and contractility at regular intervals, noting any changes in response to each drug.
Calculations
Heart Rate Calculation: Measure the number of beats in a specific time period (e.g., 1 minute) and express it as beats per minute (bpm).
Contractility Assessment: Assess contractility qualitatively or quantitatively depending on the recording apparatus. For quantitative assessment, you may need to calculate the force of contraction if the apparatus provides such data.
Sample Data Table
| Drug | Concentration | Baseline Heart Rate (bpm) | Post-Drug Heart Rate (bpm) | Baseline Contractility | Post-Drug Contractility | Observations |
| None (Control) | N/A | 60 | 60 | Normal | Normal | No effect |
| Adrenaline | 0.01 mg/mL | 60 | 80 | Normal | Increased | Increased rate |
| Atropine | 0.02 mg/mL | 60 | 40 | Normal | Decreased | Decreased rate |
| Digitalis | 0.01 mg/mL | 60 | 60 | Normal | Increased | Increased contractility |
