Animals
Two cohorts, respectively of 12 and 24 adult Lister Hooded male rats (Envigo, UK), were trained prior to surgery on reinforced T-maze alternation. The first cohort had 8 iDREADDs and 4 GFP-control animals. The second cohort had 12 iDREADDs and 12 GFP-control animals, giving totals of 20 in the iDREADDs group and 16 GFP- controls. At the time of surgery all rats weighed between 236-360g. They were housed in pairs in a temperature-controlled room, under a 12h light/dark cycle. For all behavioural experiments, water was available ad libitum . The rats were put on a food-restricted diet whereby they were still able to gain weight. None of the rats weighed less than 85% of their free-feeding weight.
All animals were randomly assigned to one of the virus conditions and underwent the same surgical and behavioural procedures. The experimenter was not, however, blind to the group membership of the animals. All experimental procedures were carried out in accordance with the UK Animals (Scientific Procedures) Act 1986 and were approved by the local Cardiff University Ethics Committee.