Male cd rats

Experiments were performed on male CD1 mice weighing 20–25 g and male CD rats weighing 200–225 g (Charles River, Italy). The animals were housed in groups of 5 mice or 4 rats in solid bottom polypropylene cages. Room temperature and relative humidity were set at 22±2°C and 55±15%, respectively, and the lighting was controlled on a cycle of 12 hour light and 12 hour darkness. Food and water were freely available, except during the experimental procedure. All experimental sessions were performed between 9:00 am and 1:00 pm to avoid diurnal variation in the behavioural tests. Each pain test was performed by an experimenter blinded to the treatments. Animals were grouped with homogeneous baseline threshold.
The experiments were carried out in accordance with the guidelines established by the the European Communities Council Directive (Directive 2010/63/EU of 22 September 2010) and approved by the National Council on Animal Care of the Italian Ministry of Health (Authorization n. 59/2013-B). All efforts were made to minimize animal suffering and to use the minimal number of animals required to produce reliable results.

Male CD rats, 350–450 g with jugular vein catheters (JVC), were purchased from Charles River (Wilmington, MA). All experiments were approved by the internal Ethical Committee for Animal Care and Use. All animals were singly housed and allowed to acclimate in house for at least 48 hours prior to study entry. The facility was kept at a temperature of 21°C, humidity of 45-55%, under a 12 hour light/dark cycle. Animals had access to food and water ad libitum.