AIM: Analgesic Effect of Morphine in Mice Using the Hot Plate Method

INTRODUCTION:

The study of analgesic effects is crucial in understanding pain management. In this experiment, we investigate the analgesic properties of morphine using the hot plate method. Morphine, a potent opioid, is known for its pain-relieving properties. By subjecting mice to a heated surface, we can observe their response time and evaluate the effectiveness of morphine in reducing pain sensitivity.

EQUIPMENT REQUIRED:

Apparatus: Eddy’s Hot plate Analgesiometer (Techno), mice cages.

Animal:  Mice (25-30 gm)

Drugs: Morphine sulphate (Dose 5mg/kg; s.c, prepare the stock solution containing 0.5mg/ml and inject 1ml/100g of body weight of mouse).

PRINCIPLE:

1. Algesia and Analgesia:
• Algesia refers to an increased sensitivity to pain stimuli, while analgesia refers to the reduction or inhibition of pain perception.
• In this method, we induce algesia in animals (such as mice) by subjecting them to a painful stimulus (heat in this case).
• Analgesic drugs are then administered to observe their effect on pain sensitivity.
2. Hot Plate Apparatus:
• The hot plate apparatus consists of a heated surface (usually maintained at a constant temperature, e.g., 55°C).
• Animals are placed on this hot plate, and their responses are monitored.
• The heat serves as the source of pain in this experiment.
3. Animal Responses:
• When placed on the hot plate, animals exhibit specific behaviours in response to the heat:

§  Jumping: Animals may jump or lift their paws due to discomfort.

§  Paw Licking: Some animals lick their paws as a reaction to the heat.

§  Withdrawal: Animals may withdraw their paws from the hot surface.

• These responses serve as indicators of pain sensitivity.
3. Experimental Procedure:
• Basal reaction time is determined by observing the animal’s initial response on the hot plate (usually within 6-8 seconds).
• A cut-off time (e.g., 15 seconds) is set to prevent paw damage.
• Analgesic drugs (e.g., morphine) are administered to the animals.
• Reaction times are recorded at different intervals (15, 30 and 60 minutes) after drug treatment.
• An increase in reaction time indicates analgesic activity.
4. Calculation and Interpretation:
• Percent increase in reaction time is calculated relative to basal values.
• If the drug prolongs the reaction time, it suggests analgesic efficacy.
• The longer the reaction time, the stronger the analgesic effect.
5. Conclusion:
• From this experiment, we can infer that the drug inhibits pain stimuli and possesses analgesic properties.
• Further studies explore dose-response relationships and safety profiles.

OBSERVATION TABLE:

INFERENCE:

*Observation table after completion of the experiment can be downloaded by clicking tab (RJPT SimLab)

DISCLAIMER: "The results provided here are only for reference or comparison purposes. Students are expected to perform the experiment and record their actual observations."

GRAPH:

PROCEDURE:

1.      Animal Preparation:

o    Weigh and mark the animals.

o    Place the animals individually on the hot plate.

o    Observe their basal reaction time (usually within 6-8 seconds) when exposed to the constant temperature (55°C).

o    Set a cutoff time of 15 seconds to prevent paw damage.

2.      Drug Administration:

o    Administer the drug (e.g., morphine sulfate) to the animals (intraperitoneally).

o    Record the reaction time of the animals on the hot plate apparatus at different time intervals (15, 30, 60, and 120 minutes) after drug treatment.

o    Consider 15 seconds as the maximum analgesia. Remove the animals from the hot plate to prevent injury.

3.      Calculation:

o    Calculate the percent increase in reaction time compared to basal values.

RESULT:

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