Oxytocin and serotonin and their roles in pre-pubertal social development in syrian golden hamsters

The pre-pubertal infancy stage of development is marked by numerous neurological and behavioral changes in Syrian Golden Hamsters. One of the most notable changes during this period is the onset of social behaviors including social playfighting. Social playfighting is initiated approximately two weeks postpartum and is completely abolished by mid-puberty. The neural mechanisms that underlie this behavioral change are not well understood, but previous research has identified both oxytocin (OT) and serotonin (5-HT) as possible regulators of this behavior. In the present study, immunohistochemical techniques were used to evaluate changing levels of OT and serotonin 5-HT in the developing brain with the hypothesis that both OT and 5-HT levels would increase and decrease simultaneously with the onset and decline of social playfighting. Additionally, it was predicted that injections of a 5-HT3 receptor agonist, m-Chlorophenylbiguanide hydrochloride (CBG), into hamster in late infancy would reinstated social playfighting behaviors. Contrary to the hypothesis, OT was found to continually increase in the fornix, lateral hypothalamus, nucleus accumbens, medial preoptic area, and anterior hypothalamus, while 5-HT continually decreased in the lateral septal nucleus and medial preoptic area. CBG injections did not reinstate social playfighting behaviors, however a large stress effect was observed, potentially masking any other effect. Analysis of OT and 5-HT receptors during this developmental stage is necessary for a better understanding of this neural mechanism. Further research into this topic may have important implications for animal models of autism spectrum disorders.