*2.1. Animals*

Three-week old outbred male Balb/C mice (Envigo, Holland) were housed in plastic cages with white wood chips for bedding, in a quiet room under controlled lighting (12 h day/night cycle) and temperature (22 ± 1◦C) conditions. Animals were regularly examined by veterinary doctors for their health, the maintenance of normal daily and nocturnal behavioral activities, and for criteria of increased disease burden, according to ethics standards for animal studies. The experimental protocol was conducted in accordance with the directives of the Italian Ministry of Health and complied with 'The National Animal Protection Guidelines'. The Ethics Committee for animal experiments of IZSLER (Brescia, Italy) (the "National Reference Centre for Animal Welfare" (http://www.izsler.it)), and the Italian Ministry of Health approved all of the procedures.
