Hot Plate Analgesia

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Hot Plate Analgesia Meters 





Digital set point

Built-in electronic timer

Manual/Foot switch timing operation


Base dimensions (HxWxD)

29 cm X 26 cm X 10 cm

Cylinder dimentions (RxD)

20 cm X 30 cm

Operating Temperature (ºC)

35 – 85, 0.1 step

Plate dimensions

24 cm X 24 cm

Reaction Time

3 digits, 0.1 sec increments

Power Requirements

220V, 50/60Hz


The paws of mice and rats are very sensitive to heat at temperatures which are not damaging the skin. The responses are jumping, withdrawal of the paws and licking of the paws. The time until these responses occur is prolonged after administration of centrally acting analgesics, whereas peripheral analgesics of the acetylsalicylic acid or phenyl-acetic acid type do not generally affect these responses.

The hot plate consists of an electrically heated surface. The temperature is controlled for 55° to 56 °C. 

The animals are placed on the hot plate and the time until either licking or jumping occurs is recorded by a built-in stop-watch. The latency is recorded before and after 20, 60 and 90 min following oral or subcutaneous administration of the standard or the test compound. The prolongation of the latency times comparing the values before and after administration of the test compounds or the values of the control with the experimental groups can be used for statistical comparison using the t-test. Alternatively, the values which exceed the value before administration for 50% or 100% can be regarded as positive and ED50 values can be calculated. Doses of 8 mg/kg s.c. morphine hydrochloride and 30 mg/kg s.c. codeine hydrochloride were found to be effective, whereas aspirin showed no effect even at high doses.

The hot plate test has been used by many investigators and has been found to be suitable for evaluation of centrally but not of peripherally acting analgesics. Mice as well as rats have been used. The method has the drawback that sedatives and muscle relaxants or psychotomimetics cause false positives, while mixed opiate agonists-antagonists provide unreliable results. The validity of the test has been shown even in the presence of substantial impairment of motor performance.The results of hot-plate test are often expressed as percent maximum possible effect (%MPE).


Where test is the latency to response after treatment; baseline is the latency to response prior to treatment; and cut off is the preset time at which the test will be ended in the absence of a response.