The inhibition of innate or learned behaviour by association with aversive stimulation has shown to be a very useful tool for researchers working in very different fields. From the study of the interference of drug treatments on a simple learning model to the study of the physiological mechanisms beneath learning or memory, passive avoidance reflexes studies have been used.

Many models have been proposed for these studies. However, among those most widely used, that suggested by Kurtz & Pearl in 1960 (J. Comp Physiol. Phycol. 53:201-6) and later modifi ed by Bures & Buresova (J. Comp. Physiol. Phycol. 56:268-62, 1963) is proven. In this model, sometimes called ‘One-trial learning’, ‘Two-compartment test’ or ‘Memory test’ it is intended to inhibit, by aversive stimulus, the rodents tendency to abandon large, open and brightly illuminated spaces so as to hide in small dark ones.

The model has a set of variables of easy determination and control (i.e. entrance to the small compartment latency), offering, at the same time, an ample parameters spectrum whose effect can be studied (v. gr. the interval between the aversive stimulation and the retention test).

Passive Avoidance studies can be carried out by means of two different types of Experimental Chambers:
A) That comprised of two differently sized enclosures, a big wihte one and a small black one, according to the original design.
B) The classic Shuttle Box with the addition of a guillotine door.

A	B

In both types of experimental chambers, the animal’s position is detected by using weight gauges.This system, which uses high sensitivity weight transducers that range from 10 to 800 grams, provides more effective and reliable detection of animal responses (zones entries) than systems based on photocells beams or on grid floor displacements.

Cages Control

Both models of passive avoidance cages may be controlled either by a Programmer or by Software. The first option is unexpensive and recommended for one single box setups, while the second is suitable for controlling a number of boxes simultaneously. Typical working protocol involves timing of transitions, i.e. time that the animal takes to move from one zone (white and ample in the traditional shuttle box) to the other, where it will get an electric shock. Under normal conditions, the subject will take longer time to move into this zone, or even it will refuse to enter (memory).

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