Tetrad test

The tetrad test for cannabinoid behavior was developed by the Martin laboratory [Little PJ, Compton DR, Johnson MR, Melvin LS, Martin BR (1988) Pharmacology and stereoselectivity of structurally novel cannabinoids in mice. J Pharmacol Exp Ther 247: 1046–1051.] for screening compounds that induced cannabinoid effects in mice. The four behavioral components of the tetrad are spontaneous activity, catalepsy, hypothermia, and analgesia. These components are tested are as follows:

* Spontaneous activity (or hypomotility) is determined by an open field test, in which a mouse is placed in a cage with perpendicular grid lines, usually spaced by ~1 inch. An experimenter counts the number of line crossings by the mouse in a given amount of time.
* Catalepsy is determined by the bar test. The mouse is placed on a bar oriented parallel to and approximately 1 inch off of the ground. If the mouse remains immobile on the bar for typically > 20 seconds, it is considered cataleptic.
* Hypothermia is determined by using a rectal probe to measure the rectal temperature.
* Analgesia is usually determined by the hot plate or tail immersion test. In the hot plate test, the mouse is placed on a heated plate, typically between 54 and 58 deg C. An experimenter measures the time it takes for the mouse to jump off of the hot plate. In the tail immersion test, the mouse is immobilized and its tail is placed into a warm water bath, typically also between 54 and 58 deg C. An experimenter measures the time it takes for the mouse to remove its tail from the water bath.

Direct CB1 agonists, such as THC (the psychoactive component of marijuana), or WIN 55,212-2, will have effects in all components of the tetrad and induce hypomotility, catalepsy, hypothermia, and analgesia in mice.

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