Browsing by Subject "Hamsters"
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Item Bacteriophage therapy of Clostridium difficile induced intestinal disease in a hamster model(Texas Tech University, 1998-12) Ramesh, VijayashreeNot avaiableItem The development of agonistic behavior in male golden hamsters : from behavior to brain(2008-08) Taravosh-Lahn, Kereshmeh; Delville, YvonIn male golden hamsters, puberty is marked by dramatic changes in agonistic behavior. Attack frequency gradually decreases as agonistic behavior evolves from play fighting to adult aggression. Attack types change as targets of attack mature from play fighting to adult attacks. In adult hamsters, serotonin plays an inhibitory role in aggression. Thus, the decline in attack frequency during puberty could be associated with an up-regulation of the activity of the serotonergic system. In adults, acute Fluoxetine treatment inhibited aggressive behavior at all doses. In juveniles, only the highest dose reduced attack frequency. Interestingly, juveniles treated with the lowest dose showed an increase in aggressive behavior. Attack type was also affected as treatment with Fluoxetine accelerated the maturation of attack targets. This same effect had been observed in previous studies in response to chronic social stress and dexamethasone treatment. Consequently, the role of cortisol on the development of the serotonergic system was also investigated. Furthermore, the density of serotonin innervation in the anterior hypothalamus and medial amygdala was found to be higher in adults than juveniles and consistent with the inhibition of attacks by the high dose of Fluoxetine. However, the differential effects of Fluoxetine at the lower doses were investigated through analysis of different serotonin receptor subtypes. In adult hamsters, aggression can be facilitated by activation of 5-HT₃ receptors and inhibited by 5-HT[subscript 1A] receptors. During puberty, the density of immunoreactive 5-HT1A receptors increased in the anterior hypothalamus and medial amydala while 5-HT₃ receptor immunoreactivity did not change. Thus, it is possible that in these areas the ratio of 5-HT₃ to 5-HT[subscript 1A] receptors decreases during puberty. This change is consistent with the decline in the frequency of offensive responses during puberty. The functionality of 5-HT[subscript 1A] and 5-HT₃ receptors on offensive aggression in juveniles was tested via peripheral injections of a 5-HT[subscript 1A] receptor agonist and a 5-HT₃ receptors antagonist. At the high dose, both drug treatments inhibited attack frequency and attack repetition. Together, these data examine the role of the serotonergic system on the development of agonistic behavior.Item Oxytocin and serotonin and their roles in pre-pubertal social development in syrian golden hamsters(2014-12) Edgar, Emma Marie; Delville, YvonThe 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.