Automated shuttle box

The active avoidance test was performed from P35 to P38, following the method described by Ichinohashi et al. (25 (link)) using the same equipment. Each rat underwent 20 daily sessions of a shuttle avoidance test for 4 consecutive days. The test was conducted in an automated shuttle box (Med Associates Inc., St. Albans, VT, USA), which was divided into two compartments with independently electrified stainless steel bars as a floor. Each session consisted of presenting a buzzer tone and light stimulation (conditioning stimulus, CS) and an electric shock (unconditioned stimulus, US). Both the CS and the US were presented for 5 s, and the US consisted of a positive half-wave constant current of 0.5 mA. Upon presentation of the CS, the rat could avoid the US by escaping to the other compartment of the shuttle box, thus switching off the CS. The interval between each trial varied from 10 to 90 s (30 s on average). The parameters were analyzed using the MED-PC IV software (Med Associates Inc.,). The avoidance proportion, i.e., the number of sessions in which the rat successfully switched off the alert and avoided electric shock, was evaluated each day.

An active avoidance test was performed to evaluate fear-motivated associative learning and memory, as previously described (17 (link), 22 (link)). The test was conducted on PND 49 in an automated shuttle box (Med Associates Inc., St. Albans, Vt., USA). The test consisted of 10 trials of conditioned stimulus (light and buzzer tone) and aversive unconditioned stimulus (foot shock). The average interval time between each trial was 30 s, ranging from 10 to 90 s. Over repeated trials, the rats learned to avoid an aversive stimulus by changing the shuttle box. The parameters were analyzed using the MED-PC IV program (Med Associates Inc.). Learning performance was evaluated using the avoidance rate in six consecutive sections.