Animals
Experiments were conducted with male mice of the C57BL/6J (BL/6) strain, and male offspring of Fos-TRAP2+/+ sires (Fostm2.1(icre/ERT2)Luo /J; IMSR_JAX:030323) and Ai14+/+ dams (B6.Cg-Gt(ROSA)26Sortm14(CAG-tdTomato)Hze/J; IMSR_JAX:007908), that were therefore of genotype Fos-TRAP2+/- x Ai14+/-and are referred to as strain Fos-TRAP2. All experimental mice were bred in-house, weaned with same-sex littermates at age 4 weeks, and maintained in littermate pairs from age 5-6 weeks until the end of the experiment, unless stated otherwise below. Mice were maintained in cages measuring 33 × 21 × 14 cm in an individually ventilated caging (IVC) system. Temperature was kept at 21-23 °C and humidity at 50-60 % and the light cycle was reversed with lights off at 07:00-19:00 h. Mice were fed ad libitum with food pellets (Complete pellet, Provimi, Kliba AG, Kaiseraugst, Switzerland) and water was also provided ad libitum. All experimental procedures were conducted during the dark phase and between 09:00-17:00 h. Each experiment began with the handling of each mouse for 5 min per day on each of 3-5 consecutive days. All experiments were conducted under an animal experiment license issued by the Veterinary Office of Canton Zurich (ZH-155/2018).