Hot plate analgesiometer

Screening of analgesic drugs

1. Hot Plate analgesiometer Presenter :- Dr Arun Singh Second Year Resident Doctor Department of Pharmacology SMS Medical College,Jaipur

2. Introduction The tested are done with the help of hot plate are used in basic pain research and in testing the analgesics property of drug and theirs's efficacy. The hot plate test is also a quick and relatively inexpensive way to assess acute thermal pain. It was proposed by Eddy and Leimbach in 1953.

3. Parts of Hot Plate Instrument

4. Hot plate meter is enabled with built in timer and foot switch. Built in timer- precisely helps to maintain the cut of time i.e., the time of contact between rodent paw and thermal plate. It prevents further damage to rodent biological tissues. Foot switch- Enable researcher to regulate the digital operations even after his hands are engaged in handling of animal. Thus, operator can instantly stop timer easily and conveniently with help of foot switch.

5. Hot plate instrument is enabled with electronic thermostat which maintains the precise temperature of plate Temperature is displayed on wide digital screen. Plexiglass chamber over the thermal plate provides safety to the researcher. The thermal plate has an advantage to maintain the uniform temperature over its surface. The front panel timer displays the number of seconds the animal took to react.

6. Screening of analgesic drug effects by Hot Plate Method The hot plate test is a test of the pain response in animals, similar to the tail flick method. Both hot plate and tail-flick methods are used generally for centrally acting analgesic, while peripherally acting drugs are ineffective in these tests but sensitive to acetic acid-induced writhing test. Pain sensitivity is recorded at 55℃ usually Although, Hot plate instrument has facility to change the temperature upto desire level (Max- 540℃ )

7. Rationale and Purpose Principle:- When rodents are placed onto a hot surface, they will initially demonstrate the aversive effects of the thermal stimulus (Pain by heat) by licking their paws and ultimately by overt attempts to escape the environment (jumping). Substances that alter nociceptive threshold either increase the latency (Reaction Time) to licking/jumping (analgesic effect) or decrease it (hyperalgesia effect). Animal reaction time is a measurement of animal resistance to pain and is used to measure efficacy of analgesics.

8. Requirements Animals: Mice (20-25 g) or Male Sprague-Dawley Rat (150-180 g) Drugs: Morphine sulphate (5mg/kg), inject I.P. 1 ml/100mg body weight Other drugs: Pentazocine (20mg/kg, i.p.), Aspirin (100mg/kg, p.o.) Equipment: Eddy’s hot plate (55 °C heat for painful stimulus ) analgesiometer

9. Procedure Mice (18-22g) are used, reared in lab. for some days & acclimatise it The temperature of the plate is maintained is 55 °C to 56 °C The animal are placed on the hot plate & time until either licking or jumping occurred is recorded The latency is recorded before & after 20,60 and 90 min. after the administration of standard or test compound

10. Observation Table

11. Conclusion From this experiment, we can conclude that, the drug inhibits pain stimulus or not and drugs has analgesic property or not.