Browsing by Author "Russell, Vivienne A"

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    Developmental stress elicits preference for methamphetamine in the spontaneously hypertensive rat model of attention-deficit/hyperactivity disorder
    (BioMed Central, 2016-06-17) Womersley, Jacqueline S; Mpeta, Bafokeng; Dimatelis, Jacqueline J; Kellaway, Lauriston A; Stein, Dan J; Russell, Vivienne A
    Background: Developmental stress has been hypothesised to interact with genetic predisposition to increase the risk of developing substance use disorders. Here we have investigated the effects of maternal separation-induced developmental stress using a behavioural proxy of methamphetamine preference in an animal model of attentiondeficit/hyperactivity disorder, the spontaneously hypertensive rat, versus Wistar Kyoto and Sprague–Dawley comparator strains. Results: Analysis of results obtained using a conditioned place preference paradigm revealed a significant strain × stress interaction with maternal separation inducing preference for the methamphetamine-associated compartment in spontaneously hypertensive rats. Maternal separation increased behavioural sensitization to the locomotor-stimulatory effects of methamphetamine in both spontaneously hypertensive and Sprague–Dawley strains but not in Wistar Kyoto rats. Conclusions: Our findings indicate that developmental stress in a genetic rat model of attention-deficit/hyperactivity disorder may foster a vulnerability to the development of substance use disorders.
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    Effect of age and unilateral dopamine depletion on striatal NMDA receptor function
    (2005) Khoboko, Thabelo; Russell, Vivienne A; Kellaway, Lauriston
    Includes bibliographical references.
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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 effect of light on a rat model of depression
    (2014) Mtintsilana, Asanda; Russell, Vivienne A; Dimatelis, Jacqueline J
    Background: Depression is a debilitating mood disorder, negatively affecting an individual’s health and well-being. Despite this, the aetiology of depression remains poorly understood. Consistently, depression treatments are far from satisfactory due to limited efficacy and adverse side effects often associated with them, suggesting a need to improve the current animal models of depression in order to understand the basic mechanisms of the disorder. In an attempt to elucidate the pathophysiology of depression, a rodent model of depression (maternal separation, MS) is used to study the neurobiological mechanisms implicated in depression. However, MS alone produces inconsistent findings and often additional stressors are used to exaggerate the effects of MS. To create a more robust model of MS, MS rats were exposed to chronic constant light (CCL). However, contradictory findings have been reported with CCL. Aims: This study aimed to explore the effects of additional CCL in an MS model by measuring glutamate and potassium-stimulated [3H]DA release in the nucleus accumbens (NAc), testing the effects of CCL on serotonin (5-HT) levels in the hypothalamus and prefrontal cortex (PFC) and measuring ì-opioid receptor (MOR-1) levels in the NAc and orexin receptor (OXR-1 and OXR-2) levels in the PFC. Methods: In order to achieve these aims four experimental groups were chosen, out of which two groups; non-maternally separated (NMS) rats and maternally separated (MS) rats were exposed to CCL for 3 weeks during adolescence and the remaining two groups; NMS and MS rats were not subjected to CCL. At postnatal day 80 (adulthood), rats were decapitated and brain tissue collected for analysis of glutamate- and potassium-stimulated [3H]DA release in the NAc using in vitro superfusion. Serotonin levels in the hypothalamus and PFC were determined using Enzyme-Linked ImmunoSorbent Assay (ELISA). Western blot analysis was used to measure MOR-1 levels in the NAc, OXR-1 and OXR-2 in the PFC. Results: MS caused a significant decrease in glutamate-stimulated [3H]DA release in the NAc. In the NAc shell, CCL exposure revealed a trend towards a decrease in [3H]DA release in response to both glutamate- and potassiumstimulation. Moreover, in the hypothalamus NMS and MS rats subjected to CCL had significantly increased 5-HT levels compared to NMS and MS rats without xvii CCL exposure. In the PFC CCL had a significant effect on 5-HT levels and it was revealed that NMS CCL rats had decreased 5-HT levels compared to NMS rats. Similarly, MS CCL rats had significantly decreased 5-HT levels compared to NMS. MS and CCL did not have any significant effect on MOR-1 protein levels in the NAc. On the other hand, MS rats had increased OXR-1 and OXR-2 proteins levels in the PFC compared to NMS and MS CCL rats. Conclusion: MS decreased glutamate-stimulated [3H]DA release in the NAc. Serotonin levels in the hypothalamus and PFC were altered by the effects of MS and CCL. Furthermore, MS exposure increased OXR-1 and OXR-2 protein levels in the PFC. However, MS and CCL did not alter MOR-1 protein levels in the NAc. Therefore, this study has demonstrated that CCL exaggerated the effects of MS and created a more robust model of MS.
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    Effect of maternal separation on stress-related proteins measured in a 6-hydroxydopamine rat model of Parkinson’s disease
    (2014) Tomes, Hayley Sarah; Russell, Vivienne A; Lang, Dirk
    The developing central nervous system is especially vulnerable and research has implicated early life stress (ELS) as a potentiating factor to cell death in a rat model of Parkinson’s disease (PD). PD is a movement disorder resulting from the selective degeneration of dopamine neurons in the substantia nigra pars compacta (SNc). Dopamine neurons have been shown to exhibit mitochondrial dysfunction, oxidative stress and misfolded protein aggregation in patients with PD. Since ELS has been shown to negatively affect the nigrostriatal pathway and mitochondrial function, developmental stress may create a vulnerable microenvironment which results in a greater rate of cell death during the development of PD. Many proteins play a role in establishing a positive microenvironment that is neuroprotective, and may be good candidates for the mechanism by which ELS potentiates neurodegeneration in the PD rat model. This study aimed to investigate whether the finding that ELS increases neuronal susceptibility to 6-hydroxydopamine(6-OHDA)-induced degeneration of dopamine neurons occurs through dysregulation of the oxidative stress-related heat shock protein (HSP)25, or plasticity-related proteins, chondroitin sulphate proteoglycans (CSPGs) or Nogo-A.
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    The effect of voluntary exercise on adult hippocampal neurogenesis in maternally separated rats
    (2016) Hardcastle, Natasha Sema; Russell, Vivienne A; Lang, Dirk M; Marais, L
    Maternal separation (MS) has been shown to produce depression-like symptoms in male Sprague Dawley rats. The underlying mechanisms responsible for the development of these depression-like behaviors are unknown. However, a growing body of evidence suggests that a reduction in neurogenesis may be a key-mediating factor. Voluntary wheel running is a form of exercise that increases neurogenesis and decreases depression-like behaviour in rats. However, the exact molecular role of neurogenesis in exercise-induced antidepressant effects still remains unanswered. This requires new tools to explore the interact ion between exercise and neurogenesis in vivo. To this end, the novel mitotic-marker, 5-ethynyl-2'-deoxyuridine (EdU), and Ki-67, an endogenous marker of cell proliferation, was characterised in order to study neurogenesis in an MS rat model of depression. Furthermore, this study aimed to provide insight into the effect of voluntary exercise on cell genesis and survival. To characterise EdU labelling of cells in vivo, male Sprague Dawley rats (Characterisation rats n =13) were injected with 50 mg/kg EdU a s noted in the literature. The optimal time point to inject the EdU label to measure mitotic activity was found to be post-natal day (PND) 60. MS or non-maternal separation (NMS) was conducted from PND 2-14 on experimental rats (n=39). From PND 54 - 74, ex perimental rats were housed in cages with attached running wheels (R) or locked running wheels (NR). All experimental rats were injected with 50 mg/kg EdU on PND 60 and transcardially perfused on PND 74 using Phosphate Buffered Saline (PBS) followed by fre sh 4% paraformaldehyde. Whole brains were then removed from the skull and placed in 4% paraformaldehyde for three hours. The brains were transferred to a 30% sucrose solution, stored in sucrose for 3-5 days and thereafter mounted in optimal cutting mediu m (OCT) and sectioned using a cryostat. Brain sections of 40 μm from 6.96 to 5.52 mm anterior to the inter-aural line were taken as dorsal and 50 μm sections from 3.84 to 2.76 mm were analyzed as ventral. The marker, EdU was detected in rat brains using t he Click-iT EdU Alexa Fluor 488 detection kit. Three molecular marker combinations were used to detect different factors for both dorsal and ventral hippocampi: (1) EdU/GFAP/NeuN, to establish how many EdU labelled cells survive to become neurons or astroc ytes (2) EdU/DCX to determine how many EdU labelled cells that have survived for 14 days are immature neurons and (3) Ki-67/DCX to indicate how many mitotically active cells are immature neurons on PND 74. Brain sections were then scanned using a confocal microscope whereby EdU stained nuclei were manually counted and cell phenotypes identified. The molecular marker combination one and two revealed no differences between treatment groups in the number of EdU-labelled cells in the dorsal and ventral hippoca mpi. However, a significant correlation was found between EdU/GFAP positive cells and EdU/NeuN positive cells in the ventral hippocampus when all treatment groups were pooled (r = 0.82, n=18, p < 0.0001). The third molecular marker combination revealed sig nificant differences in neurogenesis between groups. The MS+R group had fewer dorsal hippocampal Ki-67/DCX cells relative to NMS+R and NMS+R had significantly higher Ki-67/DCX cell count relative to NMS+NR rats. In the ventral hippocampus MS+R rats had few er Ki-67/DCX cells compared to NMS+R rats. The link between neurons and astrocytes in the ventral hippocampi corresponds with reports that an increase in neurons is linked to the presence of astrocytes. However, it may also be due to unavoidable variation in the intensity of the stain. The third molecular marker combination (Ki-67/DCX) revealed the most significant finding of this study. It showed that voluntary wheel running significantly increased the number of Ki-67/DCX co-labelled neurons in the dorsal hippocampus of NMS+R rats relative to NMS+NR which is in agreement with the literature that suggests exercise increases neurogenesis. The literature also reports that stress decreases neurogenesis and interestin gly MS+R rats had a lower cell count than NMS+R rats. This may indicate an interaction between early life stress and exercise-induced neurogenesis. This finding further suggests that MS alters neurogenesis in adult life and attenuates the effect of exercis e on the ventral hippocampus.
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    The effects of early developmental stress and exercise intervention on neurodegeneration in a rat model of Parkinson's disease
    (2010) Warton, Fleur L; Russell, Vivienne A
    Early developmental stress has been shown to produce numerous deleterious effects, e.g. the later development of affective disorders, and this has been related to chronic enhanced hypothalamic-pituitary-adrenal axis activity. Animal studies have shown that maternally separated rats exhibit increased anxiety- and depression-like behaviour in adulthood, although other evidence shows hyperactivity and impulsivity in such cases. Given that stress has these behavioural effects, it is of interest to determine whether early developmental stress might enhance the toxicity of a later unrelated neural insult. The 6-hydroxydopamine (6-OHDA) model of Parkinson's disease involves the selective unilateral lesion of nigrostriatal dopamine neurons. In this group of studies it was hypothesized that maternal separation might enhance the toxic effects of 6-OHDA.
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    Locus-coeruleus norepinephrine system function in a developmental animal model of schizophrenia: the socially isolated rat
    (2017) Atmore, Katherine H; Howells, Fleur M; Russell, Vivienne A; Stein, Dan J
    Introduction: Schizophrenia is a chronic, debilitating mental disorder characterised by positive, negative and cognitive symptoms. Current treatment regimens fail to adequately address the cognitive and negative symptoms of the disorder. Social isolation rearing (SIR) is a well-established developmental adversity paradigm which is used as an animal model of schizophrenia and usually studied in male rats. Previous SIR studies have found attentional abnormalities in isolated rats in behavioural tests which correspond to the results of studies investigating the cognitive symptoms of schizophrenia in patient trials. Isolated rats also display abnormal social responses which may be of relevance to the negative symptoms of schizophrenia. The primary aim of this study was to build on existing SIR literature by performing behavioural tests in socially isolated rats to address attentional function. Neurochemical investigations were performed on projections of the locus coeruleus norepinephrine system, known to be involved in attentional function, as research on this system is surprisingly sparse. The secondary aim of the study was to address the negative symptoms of schizophrenia using ultrasonic vocalisation recording to investigate the calling behaviour of isolated rats in response to a novel context. The study included both male and female rats so that sex differences could be studied in the context of social isolation. Methodology: Sprague-Dawley rats were weaned at postnatal day (p) 21 and randomly allocated to one of four housing groups; female socialised (n=50), female isolated (n=50), male socialised (n=38) and male isolated (n=38). Socialised animals were housed 4 per cage (single sex) and isolated animals were housed alone. Animals were weighed and cages cleaned weekly as part of a minimal handling protocol required for SIR. After 8 weeks in their housing conditions (p78-82) rats underwent one of two behavioural paradigms: three phase novel object recognition or ultrasonic vocalisation recordings. Between p90-94 animals were rapidly decapitated and the hippocampus and prefrontal cortex were dissected out for use in one of two neurochemical analyses. For in-vitro superfusion experiments the tissue was used immediately to quantify functional release of radioactively-labelled norepinephrine when stimulated with glutamate under varying conditions. Enzyme linked immunosorbent assays (ELISA) and bicinchoninic acid (BCA) protein assays was performed to quantify norepinephrine and glutamate concentrations expressed in relation to the wet weight of the tissue and amount of protein in the tissue. Results: Behavioural and neurochemical changes were induced by the SIR model. Isolated animals were found to respond to novel objects abnormally compared to control animals. During initial exposure to a novel environment in the first phase of the novel object recognition test isolated animals demonstrated hypoactivity. An overall reduction in the fractional release of norepinephrine when stimulated with combinations of glutamate and gamma-aminobutyric acid (GABA) was demonstrated in the hippocampus of isolated rats. Sex differences were evident in a number of experiments. Female rats were found to be hyperactive in the three phases of the novel object recognition test compared to males and also had elevated hippocampal norepinephrine activity as well as an increased concentration of norepinephrine in this area. Male rats on the other hand had an elevated prefrontal cortex norepinephrine activity and concentration. Conclusion: The SIR paradigm is able to induce behavioural and neurochemical changes in both female and male rats. The results of this study reinforce the usefulness of SIR as a model for schizophrenia as the way in which isolated animals responded to novel objects was different to their socialised counterparts. This difference implies an abnormal attentional response which corresponds to the cognitive symptoms described in schizophrenia. Furthermore, the neurochemical experiments performed in this study are the first of their kind and provide preliminary evidence for the GABAergic mechanisms underlying attentional abnormalities associated with SIR. The prevalence of sex differences throughout testing also provides strong evidence for the inclusion of both sexes in future studies to avoid the omission of potentially important findings. Future studies to refine and build on neurochemical analyses in developmental models of schizophrenia, such as SIR will potentially provide a mechanistic understanding of cognitive dysfunction as well as useful translational information for treating the human disorder.
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    Methamphetamine and cocaine effects on dopamine neurons in a rat model of developmental stress and attention-deficit/hyperactivity disorder
    (2014) Womersley, Jacqueline Samantha; Russell, Vivienne A; Kellaway, Lauriston; Stein, Dan J
    Attention-deficit/hyperactivity disorder (ADHD) is a developmental disorder characterised by age-inappropriate levels of inattention, hyperactivity and impulsivity and is theorised to be caused by dopaminergic dysregulation. Developmental stress interrupts vulnerable periods of neural developmental and has also been found to induce disturbances in dopamine. ADHD and developmental stress are both associated with a higher risk of abusing psychostimulants; drugs that act on the dopaminergic system to elicit a sense of reward. Central to dopamine regulation is the dopamine transporter (DAT), which is responsible for the rapid reuptake of released dopamine and therefore the regulation of extracellul ar dopamine concentration. The aim of this study was to examine the effects of developmental stress and psychostimulant exposure on dopaminergic function, more specifically DAT, in a rat model of ADHD, the spontaneously hypertensive rat (SHR) versus Wistar Kyoto (WKY) and Sprague-Dawley (SD) control strains.
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    Perceived mental effort correlates with changes in tonic arousal during attentional tasks
    (2010) Howells, Fleur M; Stein, Dan J; Russell, Vivienne A
    Background: It has been suggested that perceived mental effort reflects changes in arousal during tasks of attention. Such changes in arousal may be tonic or phasic, and may be mediated by the locus-coeruleus norepinephrine (LC-NE) system. We hypothesized that perceived mental effort during attentional tasks would correlate with tonic changes in cortical arousal, as assessed by relative electroencephalogram (EEG) band power and theta/beta ratio, and not with phasic changes in cortical arousal, assessed by P300 amplitude and latency. Methods: Forty-six healthy individuals completed tasks that engage the anterior and posterior attention networks (continuous performance task, go/no-go task, and cued target detection task). During completion of the three attentional tasks a continuous record of tonic and phasic arousal was taken. Cortical measures of arousal included frequency band power, theta/beta ratios over frontal and parietal cortices, and P300 amplitude and latency over parietal cortices. Peripheral measures of arousal included skin conductance responses, heart rate and heart rate variance. Participants reported their perceived mental effort during each of the three attentional tasks. Results: First, changes in arousal were seen from rest to completion of the three attentional tasks and between the attentional tasks. Changes seen between the attentional tasks being related to the task design and the attentional network activated. Second, perceived mental effort increased when demands of the task increased and correlated with left parietal beta band power during the three tasks of attention. Third, increased mental effort during the go/no-go task and the cued target detection task was inversely related to theta/beta ratios. Conclusion: These results indicate that perceived mental effort reflects tonic rather than phasic changes in arousal during tasks of attention. We suggest that perceived mental effort may reflect in part tonic activity of the LC-NE system in healthy individuals.
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    A Role for glutamate and Gaba in attention-deficit/hyperactivity disorder: a study of the spontaneously hypertensive rat
    (2014) Sterley, Toni-Lee; Russell, Vivienne A; Howells, Fleur M
    Attention-deficit/hyperactivity disorder (ADHD) is a heterogeneous, developmental disorder characterised by behavioural symptoms of inattention, hyperactivity, and impulsivity. The present thesis investigated how the main excitatory and inhibitory neurotransmitters in the brain, glutamate and GABA respectively, play a role in the dysregulation of the norepinephrine system in a rat model of ADHD, the spontaneously hypertensive rat (SHR), compared to its control strain, the Wistar-Kyoto rat (WKY), and a third comparator strain, Sprague-Dawley rats (SD). Release of radio-actively labelled norepinephrine from hippocampal slices of SHR, WKY, and in some experiments SD, by glutamate, GABA, potassium, and nicotine, were measured, and the involvement of glutamate and GABA receptors and transporters in the stimulated release of hippocampal norepinephrine were investigated, using an in vitro superfusion technique. Since early life stress has been shown to increase the risk of developing ADHD, the present thesis also investigated how a model of early life stress (maternal separation) affects behavioural responses to novelty (behavioural assays), plasma corticosterone (ELISA kit), and neurochemical regulation of hippocampal norepinephrine release by glutamate and GABA (in vitro superfusion) in SHR, as well as in control strains. Effects of early life stress on hippocampal protein profile of SHR, WKY and SD were also investigated using proteomic analysis, followed by Western blot analysis to confirm main proteomic findings related to the glutamate transporter GLT-1, and the potassium-chloride co-transporter KCC2. The main findings of the present thesis were that glutamate-stimulated release of norepinephrine was elevated in SHR hippocampus compared to WKY and SD, and was via glutamate AMPA receptors. Elevating tonic levels of GABA in WKY and SD hippocampi increased glutamate-stimulated release of hippocampal norepinephrine to be equivalent to that of SHR, while elevating tonic levels of glutamate in SHR hippocampus reduced glutamate-stimulated release of hippocampal norepinephrine to be equivalent to that of control strains, suggesting that GABA tonic levels are reduced while glutamate tonic levels are elevated in SHR hippocampus in vivo compared to control strains. GABAA receptor inhibition of norepinephrine release, and GABA evoked release of norepinephrine, was reduced in SHR hippocampus compared to WKY. Nicotine stimulated release of norepinephrine was reduced in SHR, compared to WKY and SD, and lacked a GABAA receptor component that was evident in WKY hippocampus. Proteomic analysis showed that the expression of the glutamate transporter GLT1b splice variant and KCC2 was increased in SHR hippocampus compared to WKY, while GLT1 total was reduced in SHR hippocampus compared to WKY and SD. Experiencing early life stress did not influence behaviour of SHR, and had limited effect on the behaviour of WKY, suggesting that SHR may be resilient to the long -term behavioural effects of early life stress. Early life stress did, however, increase NMDA receptor- and GABAA receptor-mediated inhibition of locus coeruleus-norepinephrine varicosities in SHR hippocampus, while reducing the role of these receptors in WKY hippocampus. Early life stress increased GLT1 expression in all 3 strains and reduced the GLT1b splice variant in SHR hippocampus only. These neurochemical changes following early life stress possibly involved adaptations that prevented long-term changes in behaviours of these rats. In conclusion, the results of the present thesis provide evidence supporting a role for glutamate and GABA dysfunction in the hippocampus of an animal model of ADHD, SHR, and also provide evidence for altered glutamate and GABA neurotransmission in the hippocampus of SHR following early life stress.
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    A study of an animal model of Attention-Deficit/ Hyperactivity Disorder using in vivo chronoamperometry and behavioural responses to methylphenidate and guanfacine
    (2010) Hsin-Wen Hsieh, Jennifer; Russell, Vivienne A
    Attention-Deficit/Hyperactivity Disorder (ADHD) is a childhood disorder that is behaviorally characterized by developmentally inappropriate levels of inattention, impulsivity and hyperactivity. Among several hypotheses of ADHD etiology the prevailing hypothesis implicates a hypodopaminergic system due largely to the successes of the use of psychostimulants such as methylphenidate, that increase extracellular levels of dopamine (DA) and/or norepinephrine (NE) for the treatment of symptoms. In this study, the spontaneously hypertensive rat (SHR), the most widely accepted model for ADHD, is compared with the Wistar-Kyoto (WKY) and Sprague-Dawley (SD) rat strains as controls
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    A study of glutamate receptor function in the rat barrel cortex
    (2001) Lehohla, Molupe; Russell, Vivienne A; Kellaway, Laurie A
    Bibliography: leaves 137-156.
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    A study of the WKY as a rat model of depression
    (2015) Van Zyl, Petrus Jurgens; Russell, Vivienne A
    Major depression is a heterogeneous neuropsychiatric disorder with a significant genetic - stress interaction. The Wistar - Kyoto (WKY) rat displays hypersensitivity to stress and depression - like behaviour and is used as a genetic model of major depression. However, the depression - and anxiety - like behaviour of WKY has not yet been compared between the WKY/NCrl and WKY/NHsd substrains when characterizing WKY as a rat model of depression. WKY rats respond to noradrenergic and dopaminergic drugs but not to selective serotonin reuptake inhibitors (SSRIs) and are therefore suggested to model treatment resistant depression. The early life stress of maternal separation (MS) has been used to produce a rodent model of depression in Sprague - Dawley (SD) rats but results have been variable. It was therefore considered that WKY subjected to MS might produce a more robust model of depression than either WKY or MS alone. The widely used MS SD rat model of depression, as well as MS SD rats subjected to restraint stress in adult life, were evaluated as appropriate comparator models of depression. Furthermore, changes in the biochemistry in relevant brain areas of MS SD rats exposed to restraint stress in adulthood is still elusive and was further explored. The glutamate N - methyl - D - aspartate (NMDA) receptor antagonist, ketamine, has been found to be clinically useful. The acute effects of ketamine have not been previously tested in male WKY or MS SD rats and it was therefore decided to study the behavioural effects of ketamine in these rat models of depression. The aim of the first study was to characterize the WKY rat model of depression and to select the appropriate substrain of WKY best suited as a model of depression. The WKY/NCrl and WKY/NHsd substrains of WKY were tested for optimal depression - /anxiety - like behaviour in the forced swim test (FST), open field test (OFT) and elevated plus maze (EPM) and compared to the Wistar reference strain. Both WKY/NCrl and WKY/NHsd were less active than Wistar rats in the OFT and FST and WKY/NCrl were les s activ e than WKY/ NHsd. Therefore, the initial study identified WKY/NCrl as the appropriate substrain of WKY to model depression. The WKY/NCrl rats were further characterized in terms of their response to an optimal dose of the antidepressant drug, desipramine in the FST. Desipramine has been shown to be effective in reducing the depression - like behaviour of WKY and was therefore chosen as the antidepressant drug for this study. A dose of 15 mg/kg desipramine attenuated the depression - like behaviour as evide nced by decreased immobility in the FST and was therefore used for subsequent experiments. Desipramine had no effect on opioid receptors (μ - and κ - opioid receptors, MOR and KOR, respectively) , and tyrosine hydroxylase in the nucleus accumbens ( NAc ) or prefrontal cortex ( PFC ) of WKY rats.
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    The effects of prenatal and early-postnatal ethanol exposure on rat brain neurochemistry and behaviour
    (2018) Swart, Patricia Cathryn; Russell, Vivienne A; Dimatelis, Jacqueline J
    Foetal alcohol spectrum disorder (FASD), the umbrella term used to describe the wide range of cognitive and behavioural deficits observed after exposure to alcohol in utero, is a major public health issue specifically in South Africa. South Africa is thought to have the highest prevalence of FASD in the world. FASD presents as a variety of learning and memory deficits as well as psychological disorders such as anxiety and depression but the underlying mechanisms are largely unknown and poorly understood. FASD, learning and memory processes and psychological disorders have been associated with changes in neural plasticity. Therefore, the research reported in this thesis describes ethanol-induced changes in neuroplasticity-related proteins, with specific reference to the extracellular signal-regulated kinase1/2 (ERK1/2) and glycogen synthase kinase-3-beta (GSK3β) signalling cascades, using two different animal models of FASD. Further, to elucidate additional mechanisms underlying the deficits observed in FASD, proteomic profiles were determined in order to illustrate largescale ethanol-induced changes in proteins involved in energy metabolism, neurotransmitter signalling, redox regulation, protein metabolism and cytoskeletal structure in the rat brain. In addition, this research describes vinpocetine, a phosphodiesterase (PDE) type 1 inhibitor, as a possible treatment for disturbances caused by early exposure to ethanol and investigates the effects of additional early-life stress in animal models of FASD. The first study, using a third-trimester equivalent animal model of FASD (4 g/kg/day i.p., 12 % v/v, P4 - P9), investigated early-postnatal ethanol-induced changes in adolescent rats. The results demonstrate that significant ethanol-induced changes can occur in rats that do not display overt behavioural deficits. Specifically, early-postnatal ethanol exposure decreased ERK1/2 activation in the prefrontal cortex (PFC) and increased ERK1/2 activation in the dorsal hippocampus (DH). Proteomic analysis revealed additional region-specific changes, for example, early-postnatal ethanol exposure increased the capacity for energy production in the PFC whereas in the DH, energy-related proteins were decreased compared to non-exposed controls. The PFC of rats exposed to early-postnatal ethanol was further characterized by an increased capacity for oxidative phosphorylation coupled with decreased antioxidant capacity. In addition, there was evidence that could lead to altered redox protein signaling in the DH of ethanol rats. Vinpocetine treatment of rats exposed to ethanol during early developmentreduced ethanol-induced changes in ERK1/2 activity in the PFC and DH. Additional proteomic analysis of the ventral hippocampus (VH) demonstrated that vinpocetine also reduced postnatal-ethanol-induced changes in proteins related to energy metabolism, signaling, protein synthesis and cytoskeletal structure. Therefore, vinpocetine treatment of rats exposed to earlypostnatal ethanol in conjunction with proteomic analysis has the potential to identify novel treatment targets to reduce the effects of ethanol on the developing brain. The second animal study combined prenatal-ethanol exposure (0.066 % saccharin-sweetened, 10 % ethanol) with the maternal separation model of early-life stress (3 hours/day P2 – P14) in order to account for possible effects of early-life adversity in addition to in utero alcohol exposure. Adult rats exposed to prenatal-ethanol showed reduced weight gain, hyperactivity and a negative affective state which are characteristic of FASD. However, the combination of prenatal-ethanol exposure and early-life stress did not enhance behavioural changes. Rather, early-life stress subsequent to prenatal-ethanol exposure proved beneficial as shown by similar weight gain and activity levels to that of control rats. Similarly, early-life stress reduced prenatal-ethanol-induced increase in P-ERK1/2 signalling in both the PFC and DH. On the contrary, the combination of prenatal-ethanol exposure and early-life stress seemed to have an additive effect on protein changes in the PFC of adult rats as shown by a greater number of proteins related to energy, redox regulation, signaling and cytoskeletal structure being altered by the combination of these developmental insults. In addition, the DH appeared to be more susceptible to prenatal-ethanol exposure since a greater number of proteins were significantly changed by prenatal-ethanol exposure. However, the combination of prenatal-ethanol and maternal separation stress reduced the number of significantly altered proteins in the DH. These results further highlight the wide range and region-specific effects of prenatal-ethanol exposure on the brain and importantly demonstrate an interaction between prenatal-ethanol exposure and early-life stress. Therefore, it is important to account for the possible effects of early-life adversity when modeling FASD. Results from these 2 studies highlight the long-term effects of ethanol exposure during early development on the rat brain and behaviour. In addition, these studies describe the importance of age at behavioural testing and tissue analysis and demonstrate the complexity of modeling FASD. Importantly, results demonstrate the need to account for the possible effects of earlylife adversity when modeling FASD. Further, the results presented in this thesis highlight thebenefits of performing neurochemical analyses on rats that have not been subjected to prior stressors other than the model being investigated and further, to separately analyze functionally distinct brain regions. Both studies demonstrate long-term ethanol-induced changes in PERK1/ 2 signalling and proteins related to energy metabolism and redox regulation in the PFC and DH. These results provide a platform for future research with the potential to identify novel treatment targets. Together, the results presented in this thesis contribute valuable insight to the field of FASD and the animal models used to study this multifaceted disorder.