Rodent behavior


Actimeter (Imétronic) is composed of 8 boxes, each of them equipped with an array of four parallel horizontal infrared beams and linked to a computer allowing recordings of photocell beam breaks. 8 animals can be monitored simultaneously.


In rodents, depression-like behavior can be induced by inescapable stress such as swimming or foot shocks.
The forced swim test is a 2-day procedure: on the first day, the rodents are placed in a Plexiglas cylindrical tank filled with water during 15 min and the following day, for a second session during 5 min. A camera coupled with a computer records the animal’s behavior online through a specialized digital interface Vidéotrack (ViewPoint) and software permits to assess the immobility duration as depression index, by image analysis offline.
Learned helplessness paradigm use an enclosed shuttle box (Gemini active avoidance system, San Diego Instruments) divided into two identical compartments separated by a retractable door. A grid floor delivers a scrambled shock to either side of the shuttle box. In this paradigm, an animal is initially exposed to inescapable shock on one side of the shuttle box. When the animal is later to given shock from which it can escape, the animal fails to acquire the escape response. This escape deficit is termed learned helplessness.


72-hours sleep deprivation

REM sleep deprivation-induced hyperactivity is proposed as a model of mania. Rats are deprived of REM sleep for 72 hours by the flower pot method and are placed in activity cages in an actimeter (Imetronic, France) equipped with two infrared beams. Locomotor activity is estimated by the determination of successive beam breaks at the front and at the back and vice versa (crossovers) during a 1-hour session.


Object recognition memory

The novel object recognition task is performed in a Plexiglas Y-maze apparatus. It is based on the capacity of rodents to discriminate between a novel and a previously seen (i.e. familiar) object. Rats are exposed to two identical objects during the first (learning) trial; then, after an inter-trial interval of 24h, one of the previously explored objects (now familiar) is presented along with a novel object during the second trial. Trials are videotaped and exploration time of novel and familiar objects are scored offline.

Operant conditioning behavior tests

Through operant conditioning, the animal makes an association between a particular behavior and a consequence. The device (Skinner Box) is a chamber (Med Associates Inc) that contains a bar that the animal can press in order to obtain food as a type of reinforcement in which it is possible to record each response provided by the animal as well as the unique schedule of reinforcement that the animal was assigned. The chamber is also equipped with a light and a loudspeaker and the floor is electrified.


In rat, anxiety behavior can be triggered by several factors: individual testing (animal is separated from its social group) and agoraphobia in open spaces. Rats are individually placed in apparatus for 5 min and behavior is recorded using a video camera for offline scoring.
Elevated plus maze (EPM, Panlab) is a Plexiglas structure of two open (50×10 cm) and two enclosed (50x10x40 cm) arms elevated 65 cm above the floor.
Open field apparatus is a white square of 1 m closed by a wall of 0.4 m.
Rats spontaneously prefer the enclosed arms of EPM and periphery of the open field. Increase of time spent in the open spaces is indication of anxiolysis.