Browsing by Author "Bugarith, Kishor"

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    The effect of exercise on spatial learning and hippocampal proteins in maternally separated adult rats
    (2014) Makena, Nokuthula; Russell, Vivienne A; Bugarith, Kishor
    Repeated maternal separation (MS) has been reported to induce changes in hypothalamic-pituitary- adrenal (HPA) axis activity leading to abnormal stress responses later in life. Such alterations have also been linked to poor cognitive function. In contrast, exercise enhances cognitive function. Previously, we reported that MS improved object location memory. However, exercise had no effect on object location memory despite increases in levels of synaptophysin and phospho-extracellular signal-regulated protein kinase (pERK) in the hippocampus of non-separated-exercised rats. In the current study, the same MS technique and three-week voluntary exercise regimen were tested to determine their effect on spatial learning in young adult Sprague-Dawley (SD) rats. A total of 144 rats were either maternally separated from postnatal day 2 to 14 or designated as controls. At postnatal day 50, rats were transferred to cages with attached running wheels. Approximately half of the rats were allowed to exercise voluntarily in the wheels whilst the wheels attached to the cages of the remaining non-exercising rats were immobilised. Rats were divided into 3 cohorts. Cohort 1 provided baseline levels of pERK, mitogen-activated protein kinase phosphatase-1 (MKP-1) and brain derived neurotrophic factor (BDNF) after exercise. Cohorts 2 and 3 were trained in the Morris Water Maze (MWM) 1 and 15 days post-exercise, respectively. Consistent with our previous findings, pERK was increased in non-separated-exercised rats post-exercise. MKP-1, the regulator of pERK, was also increased in the non-separated-exercised group. BDNF was decreased in the MS non-exercised group but augmented by exercise. All groups trained immediately after exercise performed similarly in the MWM but MS rats from cohort 3 had better reversal spatial memory. According to these results, repeated MS decreased neurotrophic factors but did not alter the plasticity-related proteins measured in this study. However, this phenomenon was not associated with performance in the spatial learning and memory task in the MWM. These current observations support our previous findings that MS can cause adaptations that lead to improved learning and memory in adulthood.
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    The impact of voluntary exercise on relative telomere length in a rat model of developmental stress
    (BioMed Central Ltd, 2012) Botha, Martmari; Grace, Laurian; Bugarith, Kishor; Russell, Vivienne; Kidd, Martin; Seedat, Soraya; Hemmings, Sian
    BACKGROUND: Exposure to early adverse events can result in the development of later psychopathology, and is often associated with cognitive impairment. This may be due to accelerated cell aging, which can be catalogued by attritioned telomeres. Exercise enhances neurogenesis and has been proposed to buffer the effect of psychological stress on telomere length. This study aimed to investigate the impact of early developmental stress and voluntary exercise on telomere length in the ventral hippocampus (VH) and prefrontal cortex (PFC) of the rat. Forty-five male Sprague-Dawley rats were categorised into four groups: maternally separated runners (MSR), maternally separated non-runners (MSnR), non-maternally separated runners (nMSR) and non-maternally separated non-runners (nMSnR). Behavioural analyses were conducted to assess anxiety-like behaviour and memory performance in the rats, after which relative telomere length was measured using qPCR. RESULTS: Maternally separated (MS) rats exhibited no significant differences in either anxiety levels or memory performance on the elevated-plus maze and the open field compared to non-maternally separated rats at 49 days of age. Exercised rats displayed increased levels of anxiety on the day that they were removed from the cages with attached running wheels, as well as improved spatial learning and temporal recognition memory compared to non-exercised rats. Exploratory post-hoc analyses revealed that maternally separated non-exercised rats exhibited significantly longer telomere length in the VH compared to those who were not maternally separated; however, exercise appeared to cancel this effect since there was no difference in VH telomere length between maternally separated and non-maternally separated runners. CONCLUSIONS: The increased telomere length in the VH of maternally separated non-exercised rats may be indicative of reduced cellular proliferation, which could, in turn, indicate hippocampal dysfunction. This effect on telomere length was not observed in exercised rats, indicating that voluntary exercise may buffer against the progressive changes in telomere length caused by alterations in maternal care early in life. In future, larger sample sizes will be needed to validate results obtained in the present study and obtain a more accurate representation of the effect that psychological stress and voluntary exercise have on telomere length.