This study was carried out on 25 double BAC transgenic mice (Drd1a-tdTomato/Drd2-EGFP) of 2 month old weighing between 20–30 g. Equal numbers of male and female were used. These D1/D2 mice were generated by breeding B6SJLF1-D1tdTomato BAC transgenic mice19 with C57Bl6J-D2-EGFP BAC animals69. They allow direct identification of the D1, D2 and D1/D2 MSNs (Fig. 8). In order to minimize over expression artifacts, all mice where heterozygous for each individual BAC transgene. Animals were housed under a 12 h light-dark cycle with water and food ad libitum. All procedures were approved by the Comité de Protection des Animaux de l’Université Laval, in accordance with the Canadian Council on Animal Care’s Guide to the Care and Use of Experimental Animals (Ed2) and with the ARRIVE guidelines. Maximum efforts were made to minimize the number of animals used.
