Does orexin B infused into nucleus accumbens affect open field activity in wistar rats

Orexins, which have been located in several parts of brain particularly in the hypothalamus and parts of diencephalon were implicated role in ingestive behaviour, role in sleep, wakefulness and other modalities of activities in animals. Nucleus accumbens is a large nuclear mass involved in appetitive behaviour and addiction. In order to evaluate if the Orexinergic system in open field activity, we carried out studies by infusing Orexin B and its antagonist into nucleus accumbens, in Wistar albino rats weighing 200±20 g at the time of selection. Orexin B was infused bilaterally into Nucleus accumbens and tested in open field for time spent in the peripheral squares, central squares, defecation score, rearing, grooming. Similar recording was done following infusion of Orexin B antagonist (TCS-OX2-29) into Nucleus accumbens in the next experiment. The infusion of orexin B into nucleus accumbens rats made significantly more (p < 0.001) central square entries compared to controls. There was also a significant increase (p < 0.001) in time spent in central squares (28±0.73) compared to controls (20± 1.15). But treatment didn't show any alteration in the number of rearing, grooming and fecal excreta. The infusion of orexin B antagonist (TCS-OX2-29) into nucleus accumbens made significantly fewer (p < 0.01) central squares entries compared to controls. There was also a significant decrease (p < 0.001) in time spent in central squares compared to controls but didn't show any alteration in the number of rearing, grooming and fecal excreta. The results of this study reveal that the Orexin infusion decreased anxiety and increased exploratory behaviour in the rats.