The Randall-Selitto test or paw pressure test is a technique for the measurement of the pain response in animals. It is used in basic pain research and to test the effectiveness of analgetics by observing the reaction to gradually increasing pressure on an inflamed

Inflammation

Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...

 paw. Pain is deemed to be present if the animal starts to exhibit the flight or struggle response.

Randall and Selitto exploited the fact that inflammation increases pain sensitivity and this sensitivity is modifiable by analgesics. The inflammation may be induced by injecting a dry yeast

Yeast

Yeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with 1,500 species currently described estimated to be only 1% of all fungal species. Most reproduce asexually by mitosis, and many do so by an asymmetric division process called budding...

suspension into the underside of the hind limb.