Positive emotion-specific changes in gene expression profile in hypothalamus of the tickled rats

The changes of mRNA expression levels were analyzed in the hypothalamus of the juvenile rat stimulated by tickling for 4 weeks as a positive stimulation. The genes involved in feeding regulation were up-regulated by positive stimulation compared with light-touch stimulation, and the genes related to the stress hormone were down-regulated compared with control (no stimulus). Keywords: Stress response Twenty-one-day-old male Wistar rats　after weaning were used. All rats were separately maintained in the standard cages which were shielded with screens not to see each other during the study. The rats were then subjected to the following three conditions; tickling, light touch, and no stimulus. The stimulation was given to the rats once every weekday (Monday to Friday) for 4 weeks. Tickling stimulation was used as a mimic of the rough-and-tumble play of rats which induced a positive emotional response [50 kHz ultrasonic vocalization (USV)]. Light touch was a discriminative stimulation to tickling, and neither the rat with light touch nor with no stimulus showed such a response in general. Gene expression changes in hypothalamus of the tickled rats were comprehensively analyzed comparing with light touched and no stimulated rats using microarray techniques. Biological replicates: 4 animals each condition. One replicate per array.