In vivo

Tail flick test

The tail flick test is a test of the pain response in animals. It is used in basic pain research and to measure the effectiveness of analgesics, by observing the reaction to heat.


Most commonly, an intense light beam is focused on the animal's tail and a timer starts. When the animal flicks its tail, the timer stops and the recorded time (latency) is a measure of the pain threshold. Alternate methods can be used to apply heat, such as immersion in hot water.

Alternately, a dolorimeter with a resistance wire with a constant heat flow may be used. For the tail flick test, the wire is attached to the tail of the organism, and the wire applies heat to the tail. The researcher then records the latency to tail flick.


Researchers testing the effectiveness of drugs on the pain threshold often use the tail flick test to measure the extent to which the drug being tested has reduced the amount of pain felt by the model organism. Both laboratory mice and rats are a common model organism for these tests.

Explanatory diagram of Tail Flick Analgesiometer.

Rat hind paw oedema test

Carrageenan1-induced paw edema2 is one of the most popular tests used in the screening of African spices and vegetables for antiinflammatory activity.

1.- Carrageenan is an insoluble fibre, which is not digested and is added to various food products, except in evaporated milks. Carrageenan when ingested causes inflammation in the intestines, as well as intestinal discomfort.

2.- The presence of excess fluid in an organ or tissue of the body, which may sometimes have the appearance of a soft swelling.

First, Plethysmometer displays the exact paw volume. A model on rat paw swelling has to be made. The Plethysmometer (Paw Edema) test serves to measure the effectiveness of anti-inflammatory agents to reduce edemic conditions.

To determine and analyse whether the drug is effective, there will be needed some rats to experiment with. The rats will be divided in three groups: the ones which will be given placebo, others given the drug which is being tested and, at last, which will be given the active product or positive control, in other words, drug that it is known is effective.