Browsing by Author "Borgland, Stephanie"
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- ItemOpen AccessBehavioural and microglial effect of cannabinoids in neuropathic pain(2022-09) Davidson, Chloé E. D.; Trang, Tuan; Borgland, Stephanie; Hill, MatthewChronic pain is a disease affecting 1 in 5 Canadians and the leading cause of disability worldwide. Among the most debilitating forms of chronic pain is neuropathic pain, which is caused by injury or disease of the nervous system. Neuropathic pain is difficult to manage clinically because it is often resistant to strong analgesics including opioids. Since therapeutic options are limited, some patients resort to medical cannabis to alleviate pain symptoms. Pain is the most common medical reason to use cannabis and cannabinoids. However, the efficacy of cannabis for pain, as well as its potential health impacts, are not well defined. My project addresses this knowledge gap by characterizing the behavioural and cellular effects of cannabis in the rat spared nerve injury (SNI) model. This neuropathic pain model replicates the mechanical pain sensitivity reported in neuropathic pain patients, including mechanical allodynia, which is an abnormal sensitivity to tactile stimuli in which even light touch can elicit pain. Prior research shows that microglia, the resident immune cells of the central nervous system, play a central role in the development of chronic neuropathic pain after peripheral nerve injury in males. In this study, we assessed the effects of vaporized whole cannabis extract and a combination of THC and CBD on mechanical hypersensitivity in spared nerve injury (SNI) male and female Sprague-Dawley rats. I also investigated the effect of cannabinoid exposure on spinal microglia. I find that cannabis and cannabinoid extracts transiently reversed mechanical allodynia in the spared nerve injury model of neuropathic pain in a sex- and compound-dependent manner. Additionally, I demonstrate a compound-dependent effect of cannabinoids on microglial reactivity.
- ItemEmbargoContributions of early life adversity, sex, and traits towards compulsive opioid self-administration(2017) Hynes, Tristan; Lovic, Vedran; Dyck, Richard; Antle, Michael; Borgland, StephanieMany people try addictive drugs, but only a small percentage transition from situational/recreational use to the escalating, compulsive, and relapsing disorder of addiction. It is therefore important to characterize the individual differences that render individuals vulnerable to addiction. Substantial evidence suggests that individual differences in early life experience, biological sex, personality traits, and neurobiology of the reward system are all associated with the development of addiction. A dimensional model of how all these factors relate to addiction is necessary, but simultaneously and experimentally probing all these processes in humans is impossible. I therefore conducted a large-scale study to explore these phenomena in rats. Throughout ‘adolescence’ (PND 21-35), I exposed a group of rats to a variety of stressors [i.e., forced-swim, restraint, predator odour, food-restriction, and social isolation; termed ‘early life adversity’ (ELA)]. As adults (PND 60-140), I assessed them on numerous addiction-relevant behavioural traits (i.e., impulsivity, anxiety, novelty-preference, and attraction to reward cues). After trait assessment, I observed the rats’ propensity to self-administer the opiate remifentanil. I then killed a subset of rats and quantified DA receptor mRNA in the mPFC. ELA decreased impulsivity and decreased the rate of acquisition of opiate self-administration in male rats only. Compared to males, female rats exhibited greater anxiety-like behaviour and potentiated opioid self-administration. Anxiety-like behaviour and attraction to reward cues predicted several addiction-relevant behaviours.
- ItemOpen AccessDietary Modulators of Gut Microbiota: Impact on Metabolic Health and Behaviour(2019-07-03) Nettleton, Jodi; Reimer, Raylene; Shearer, Jane; Borgland, StephanieBackground The ability of the gut microbiota to influence metabolic health and the potential to alter behaviour has been well-established. Therefore, targeting the gut microbiota to improve its’ composition through dietary agents is an attractive strategy to improve chronic diseases, like obesity, and impaired behaviours in neurodevelopmental conditions, like autism spectrum disorder. Objective This dissertation examines how dietary additives, including low-calorie sweeteners (LCS), and probiotics, prebiotics and synbiotics can alter metabolic, microbial and behavioural outcomes in rodents. Specifically, the objectives of this thesis were to: 1) assess the impact of maternal aspartame and stevia consumption on dams and offspring metabolism and gut microbiota; 2) determine the effects of long term low-dose stevia consumption in young male rats; 3) examine the impact of prebiotic, probiotic and synbiotic consumption on behaviours in an autism spectrum disorder mouse model. Methods 1) Diet-induced obese female rats consumed aspartame or stevia alongside a high fat diet during gestation and lactation; 2) Young male rats consumed stevia for nine-weeks; 3) Male BTBR mice were fed diets supplemented with prebiotic, probiotic, or synbiotic for three-weeks. In the first two studies, body composition, gut microbiota composition, and glucocentric and mesolimbic reward parameters were examined in dams, offspring, and male rats. In the third study, body weight and feces were measured/collected weekly and behaviour was tested at the end of treatment. Results The primary findings from our three study objectives were: 1) Maternal LCS consumption increased body weight and impaired glucocentric parameters in early life in offspring and changes were mediated by the gut microbiota; 2) Stevia intake reduced the relative abundance of cecal bifidobacteria taxa; 3) Probiotic consumption improved sociability and repetitive behaviour whereas prebiotic worsened sociability and had mixed effects on communicative variables, yet probiotic, prebiotic and synbiotic treated mice all had alterations in gut microbiota composition that indicated potential improved gut health. Conclusion Our results provide evidence for the role of low-calorie sweeteners in perpetuating obesity by altering gut microbiota composition and the potential for probiotic, prebiotic, and synbiotic to modulate behaviours associated with autism spectrum disorder.
- ItemOpen AccessEffect of Cafeteria Diet Induced Obesity on Neuroinflammation in the Orbitofrontal Cortex(2016) Kaur, Manpreet; Borgland, Stephanie; Pittman, Quentin J.; Trang, TuanPalatable food consumption is associated with obesity and induce inflammation in brain. The orbitofrontal cortex is implicated in compulsive behavior. Glial changes lead to synaptic remodeling and altered behavior. However it is not clear if metabolic changes associated with cafeteria diet consumption lead to glial changes in OFC. My study addressed this important question whether intake of cafeteria diet leads to glial changes in OFC. I observed that rats with extended access to cafeteria diet become obese, exhibited inflexible behaviour and increased GFAP and IBA1 expression in the hippocampus and the hypothalamus. Further, there was an increase observed in several proinflammatory cytokines in the hypothalamus. My work has shown that extended intake of cafeteria diet is associated with increased GFAP expression in OFC without any changes in IBA1 expression, proliferation and the levels of proinflammatory cytokines. This is the first study reporting astrocytic activation in OFC associated with compulsive food intake.
- ItemOpen AccessThe Effects of a High-Fat Diet on Lateral Orbitofrontal Cortex Physiology and Behaviours(2023-01-06) Seabrook, Lauren Taylor; Borgland, Stephanie; Hill, Matthew; Thompson, RogerComplex interactions of internal and external factors drive overeating which leads to increased body weight and obesity. In our modern food environment, energy dense foods are typically overconsumed because they are easily accessible and highly palatable. Preclinical models of obesity have begun to examine how diet induced obesity impacts synaptic plasticity in brain regions that guide decision making and motivated feeding behavior. The orbitofrontal cortex (OFC) can influence food intake decisions as it integrates sensory information with limbic, prelimbic, and basal ganglia regions. Rats with OFC lesions consume food regardless of the updated sensory features and motivational value of the outcome, in a habit-like fashion. Given that habit-like eating is associated with obesity, it is possible that access to an obesogenic diet can influence OFC synaptic function. The lateral orbitofrontal cortex (lOFC) consists of pyramidal output neurons arranged in layers along with inhibitory GABAergic interneurons and astrocytes. Diet induced obesity alters inhibitory signaling, along with morphological changes in pyramidal neurons and astrocytes. However how pyramidal neuron disinhibition influences lOFC neuronal activity and behavior is unknown. Furthermore, how pyramidal neurons in the lOFC respond acutely to high-fat caloric dense food leading to the etiology of diet induced obesity has yet to be elucidated. Chapter 1 critically evaluates and reviews literature describing the functionality of the OFC, and the neurobiology and corresponding behaviours on the effects of a high-fat diet leading to obesity. Chapter 2 examines how diet-induced obesity disinhibits pyramidal neurons in the lOFC and biases decision making. In Chapter 3 how lOFC pyramidal neurons respond to energy status is examined, our results indicate that short- and long- term high-fat diet exposure differentially alters GABAergic signalling in the lOFC. This thesis provides insight on how consumption of a high-fat diet alters the lOFC; a brain region involved in the self-regulation of food intake. This has implications in present society as palatable caloric-dense foods are abundantly available and chronic consumption can lead to weight gain, diet induced obesity and comorbid health conditions.
- ItemOpen AccessThe effects of fasting on the physiology of ventral tegmental area neurons of male and female mice(2022-01) Godfrey, Nathan; Borgland, Stephanie; Bains, Jaideep; Hill, MatthewThe activity of dopamine neurons in the VTA controls release of dopamine in the striatum, amygdala, and cortical regions to signal reward predictions in response to an environmental cue, and to activate behaviour for reward acquisition and consumption. The activity of dopamine neurons is controlled by both GABA and glutamate inputs to the VTA. Release of dopamine at terminal regions occurs in response to firing of dopamine neurons, induced by prolonged depolarization, typically due to NMDA receptor activation by an excitatory input. Furthermore, dopamine neurons in the VTA are strongly innervated by tVTA/RMTg GABA neurons that act as inhibitory interneurons to inhibit the firing of dopamine. Removal of this inhibition can also lead to firing of dopamine neurons and release of dopamine. GABA neurons from the lateral hypothalamus (LH) send a strong projection to tVTA/RMTg GABA neurons, providing disinhibition of dopamine neurons, release of dopamine in terminal regions, and reward acquisition and consumption. VTA dopamine neurons are responsive to external factors including stress, satiety, and food restriction. However, an understanding of how synaptic inputs to these neurons change in response to acute energy deprivation is unknown. The first aim of my thesis seeks to understand how both excitatory and inhibitory synapses to VTA dopamine neurons changes in response to a 16 hour, dark-cycle fast. I found that acute fasting increases food approach and consumption of high-fat food in a sex dependent manner. These behavioural changes were paralleled by an increase in excitatory synaptic strength in males, and stronger endocannabinoid-mediated short-term synaptic depression in females. The second aim of my thesis focuses on the LH GABA input to GABA neurons in the tVTA/RMTg and how a 16 hour, dark-cycle fast affects synaptic transmission from this input and the general excitability of tVTA/RMTg GABA neurons. I found that fasting decreased the excitability of tVTA/RMTg GABA neurons. In addition, fasting decreased the strength of the LH GABA input to tVTA/RMTg GABA neurons in both males and females and decreased the probability of release at these synapses in females but not males. The knowledge gained from this research will be instrumental in understanding how acute energy deprivation affects the underlying neuronal circuits that control motivation and will aide in the development of more effective treatments for obesity and eating disorders.
- ItemOpen AccessMorphological and Activity-Dependent Effects of Astrocyte Activation in the Orbitofrontal Cortex(2022-09) Sobey, Marissa; Borgland, Stephanie; Kurrasch, Deborah; Bains, Jaideep; Gordon, GrantAstrocytes, the most abundant glial cell in the central nervous system (CNS), have significant roles in supplying energetic substrates to neurons, regulating blood brain barrier (BBB) permeability, homeostasis of ions and pH to neurons in the tripartite synapse. Much remains unknown about astrocytes due to the limitations of current tools to visualize and manipulate astrocyte activity. To understand astrocyte physiology and pathophysiology, we need methods to visualize and specifically assess the activity of astrocytes. A recent astrocyte promoter, gfaABC1D, may provide better astrocyte specificity and transduction efficiency in the cortex. S100B is a calcium-binding glycoprotein only expressed in the soma of astrocytes also can be used as a marker for astrocytes. To activate cortical astrocytes, we targeted excitatory Designer Receptors Exclusively Activated by Designer Drugs (hM3Dq DREADDs) to astrocytes of the orbitofrontal cortex (OFC), a region involved in decision making and injected the DREADD-specific, brain penetrant ligand, DCZ. I hypothesize that using a combination approach of S100B, and gfaABC1D-tagged DREADD virus will successfully label and activate astrocytes in the lateral OFC (LOFC), whilst not indirectly influencing neuronal activity (measured by cFos). This thesis used a novel IMARIS 3D visualization method to visualize astrocytes and the colocalization of the DREADD-reporter in astrocytes. The result suggests that there are more astrocytes in the LOFC compared to the medial (MOFC), independent of DCZ administration. There is intraregional heterogeneity between the LOFC and the MOFC. The gfaABC1D-DREADD virus successfully transfected astrocytes in LOFC. There was no increase in cFos intensity in NeuN cells in the LOFC or the MOFC, suggesting that activation of Gq-DREADDs in astrocytes was not sufficient to affect neuronal activation. Future research should address the calcium activity response to DCZ on excitatory DREADDS in astrocytes in-vitro. This thesis offers an acute method to assess astrocytes in the cortex to further be used in a chronic model to induce inflammation, to better understand cortical reward system inflammation seen in addiction and obesity.
- ItemOpen AccessNeural Basis of Arousal Signaling for Non-Photic Resetting of the Circadian Clock(2023-09-21) Moshirpour, Mahtab; Antle, Michael Christopher; Dyck, Richard; Spanswick, Simon; Borgland, Stephanie; Mintz, Eric M.Input to the suprachiasmatic nucleus (SCN) from the intergeniculate leaflet (IGL) is necessary for non-photic entrainment. However, the underlying mechanisms of IGL activation remain unknown. There are several arousal centers in the brain that could be involved in bringing about non-photic entrainment. These include the lateral hypothalamus (LH) which contains clock-projecting orexin cells, and the cholinergic basal forebrain that directly communicates with the SCN. Even though arousal is the key component of non-photic entrainment, the relationship between the IGL and these arousal areas is unclear. We investigated the neural basis of arousal signaling by first studying the potential inputs to the IGL from the LH and the basal forebrain of Syrian hamsters. Projections to the IGL, from both the LH and the basal forebrain cholinergic cells were found. Next, we examined whether orexin is necessary and sufficient for non-photic phase shifting by both blocking orexin prior to an arousal-inducing protocol such as sleep deprivation and administering orexin in the IGL. It was found that orexin alone is not necessary or sufficient to cause shifts. Instead, it was found that dual administration of a glutamate receptor agonist with orexin is sufficient to cause significant shifts, suggesting an additive effect at the IGL. We next examined whether acetylcholine is necessary for non-photic entrainment. No attenuation of the arousal-induced response was observed by blocking acetylcholine at the IGL, suggesting that it is not necessary for non-photic entrainment, though it has been reported to be critical at the SCN level. Finally, accumulation of the sleep factor adenosine in the basal forebrain was mimicked as a potential signal for activating the basal forebrain. No significant phase shifts or cellular activation of the basal forebrain was observed after blocking adenosine at the basal forebrain. Taken together, the results present the first report of a dual role for orexin and glutamate in potentially gating the IGL’s non-photic inputs to the SCN.
- ItemOpen AccessOrexin B/hypocretin 2 increases glutamatergic transmission to ventral tegmental area neurons(2008-10) Borgland, Stephanie; Storm, Emily; Bonci, AntonelloThe orexins (hypocretins) play a crucial role in arousal, feeding and reward. Highly relevant to these functions, orexin-containing neurons from the lateral hypothalamus project densely to the ventral tegmental area (VTA), which is the origin of dopamine projections implicated in motivation and reward. Orexin A/hypocretin 1 (oxA/hcrt-1) can enable long-term changes associated with drugs of abuse; however, the effects of orexin B/hypocretin 2 (oxB/hcrt-2) on excitatory synaptic transmission in the VTA are unknown. We used whole-cell patch-clamp electrophysiology in rat horizontal midbrain slices to examine the effects of oxB/hcrt-2 on excitatory synaptic transmission. We observed that oxB/hcrt-2 has distinct effects from oxA/hcrt-1 in the VTA. oxB/Hcrt-2 (100 nM) increased presynaptic glutamate release in addition to a postsynaptic potentiation of NMDA receptors (NMDARs). The oxB/hcrt-2-mediated postsynaptic potentiation of NMDARs was mediated via activation of orexin/hypocretin 2 (OX2/Hcrt-2) receptors and protein kinase C (PKC). Furthermore, the increase in transmitter release probability was also PKC-dependent, but not through activation of orexin/hypocretin 1 (OX1/Hcrt-1) or OX2/Hcrt-2 receptors. Finally, oxB/hcrt-2 or the selective OX2/Hcrt-2 receptor agonist ala(11)-D-leu(15)-orexin B, significantly reduced spike-timing-induced long-term potentiation. Taken together, these results support a dual role for oxB/hcrt-2 in mediating enhanced glutamatergic transmission in the VTA, and suggest that oxA/hcrt-1 and oxB/hcrt-2 exert different functional roles in modulating the enhancement of the motivational components of arousal and feeding.
- ItemOpen AccessPannexin-1-Dependent Long-Term Depression at the CA3-CA1 Synapse(2021-04-09) Werner, Allison Claire; Thompson, Roger; Trang, Tuan; Borgland, Stephanie; Wilson, Richard; Raymond, LynnLong-term depression (LTD) is a form of synaptic plasticity characterized as a long-lasting decrease in synaptic strength. It is a critical mechanism underlying learning and memory. The most commonly studied form of LTD depends on the activation of the postsynaptic glutamate receptor, NMDA receptor (NMDAR), within the hippocampus. Classically, LTD is thought to result from the influx of ions (particularly calcium, Ca2+) through the NMDAR. However, this classical model has come into question as evidence supporting non-ionotropic NMDAR signaling (i.e. “metabotropic signaling”) during LTD has increased over the past few years. Previous work in the Thompson lab has linked metabotropic NMDAR signaling to the large pore channel, Pannexin-1 (Panx1) under pathological conditions through Sarcoma (Src) kinase activation. Recently, Panx1 has been implicated in synaptic plasticity, particularly hippocampal LTD. Therefore, my overarching hypothesis for this thesis is that Panx1 acts as a downstream target of non-ionotropic NMDAR signaling during hippocampal LTD. Here I demonstrate that all components of the NMDAR-Src-Panx1 pathway are necessary for successful hippocampal LTD within the CA3-CA1 synapse following a low-frequency stimulation (LFS) of 3 Hz. Additionally, I show that Src interaction with Panx1’s C-terminal domain (CTD) is required for successful synaptic depression. Together, this supports a role for metabotropic NMDAR activation of Panx1 via Src kinase during LFS-induced LTD. Towards the end of this thesis, I begin to hypothesize and study the potential roles and contributions of Panx1 during LTD. Although still preliminary, my data suggests ATP release through Panx1 and the activation of nearby purinergic receptors, particularly P2X4 receptors (P2X4Rs), may be critical drivers of LTD downstream of NMDAR activation.
- ItemOpen AccessThe Role of Orexin in Social Behaviour(2022-09) Dawson, Matthew; Sargin, Derya; Antle, Michael; Borgland, Stephanie; Whelan, PatrickSocial behaviour is essential to the survival of most organisms and is produced by complex neural systems. The hypothalamus is known to be crucial for survival and reproduction. Recent research into the neural substrates of social behaviours has identified that hypothalamic regions play a fundamental role in the regulation of social behaviour by driving internal states of arousal, attention, and motivation. Hypocretin (Hcrt)/orexin-expressing neurons in the lateral hypothalamus (LH) are critical for the regulation of arousal and motivated behaviours. Hcrt neurons are widely studied with respect to their function in the regulation of these internal states however, there is limited knowledge for their role in social behaviour. We hypothesized that the LH Hcrt neurons have a fundamental role in social interaction and tested this hypothesis with a combination of fiber photometry and optogenetic experiments in a novel Hcrt-Cre-C57BL6/J mouse line. We found that the activity of the LH Hcrt neuron population increases following approach to social conspecifics. The increase in activity was significantly greater during approach to a novel conspecific rather than a familiar one, and in males compared to females. Using a familiar/novel object interaction test, we then determined that this differential increase was specific to social stimuli. Optogenetic inhibition of Hcrt neuron activity caused male mice to spend significantly less time socially interacting suggesting a disruption in normative social behaviour. This effect of optogenetic inhibition was absent in females. Finally, we validated that the effect of Hcrt neuron inhibition on social behaviour was not due to changes in anxiety-like or locomotor behaviours. In sum, these findings provide strong evidence for the role of hypocretin neurons in social behaviour, particularly in male mice.
- ItemOpen AccessSpatial, temporal, and circuit-specific activation patterns of basolateral amygdala projection neurons during stress(2023-07) Aukema, Robert; Hill, Matthew; Borgland, Stephanie; Bains, Jaideep; Bruchas, Michael; McGirr, AlexanderIn humans and rodents, the amygdala is rapidly activated by stress and hyperactivated in conditions of pathological stress or trauma. However, there is a striking lack of information of the anatomical specificity of amygdala subregions and circuits explicitly activated by stress, and of its role in governing typical responses to stress such as hypothalamic-pituitary-adrenal (HPA) axis activation. The overarching aim of this thesis was to conduct a systematic investigation of the spatial, temporal, and circuit-specific activation patterns of basolateral amygdala (BLA) projection neurons during exposure to acute stress. Additionally, we explicitly tested the role of the BLA in activation of the HPA axis, as this remains a poorly understood process. Chapter 1 describes how the BLA is anatomically well-situated for cognitive evaluation of emotional stimuli and describes the role of the BLA in diverse behavioural and physiological processes via efferent projections to many different brain structures. Chapter 2 identifies a common BLA subregion that is responsive to stressful stimuli, albeit with distinct temporal activation patterns, and which bidirectionally influences HPA axis activity. Chapter 3 maps the topographical distribution of six different populations of projection neurons throughout the BLA, and demonstrates that, although widely activated by stress exposure, inhibition of isolated populations does not influence HPA axis activity. Chapter 4 investigates the topographical distribution and stress-induced activation of BLA neurons expressing corticotropin-releasing hormone receptor type I (CRHR1), which, just like discrete circuits, does not influence HPA axis activity on its own. Together, this emphasizes the heterogeneity of BLA projection populations, while providing evidence that a large, diverse population of BLA projection neurons are activated by exposure to acute psychological stress.
- ItemEmbargoThe distribution of Dopamine Receptors in the Mesencephalic Locomotor Region and colocalization with inhibitory and excitatory cell types(2024-03-20) Di Vito, Stephanie; Whelan, Patrick; Wilson, Richard; Borgland, Stephanie; Lohman, AlexThe dopaminergic (DA) control of motor function has for many decades been thought to be indirect via substantia nigra pars compacta (SNc) projections to the striatum. DA interaction with dopamine D1 or D2 -receptor (D1R or D2R) expressing cells in the striatum leads to locomotion via disinhibition of Mesencephalic Locomotor region (MLR) neurons. The MLR is known to be a key centre for the control of locomotion. It comprises the cuneiform nucleus (CnF) and pedunculopontine nucleus (PPN). These regions are heterogeneous and show differential effects on locomotion following stimulation of either glutamatergic or GABAergic cells. The MLR receives predominantly inhibitory input from the basal ganglia. Recently, our lab discovered that a dopaminergic nucleus within the medial zona incerta (mZI); the A13, projects to the MLR. Direct dopaminergic projections that modulate locomotion, from the SNc to the MLR, have also been identified in lampreys and rats. This suggests at least two direct dopaminergic control pathways to the MLR that lie parallel to the canonical nigrostriatal DA pathway and modulate motor control. However, it is not well understood how dopamine receptors are distributed across cellular subtypes in the MLR. In this thesis I used adult C57BL/6 male and female mice to address this gap. RNAscope® was performed to determine the distribution of DA receptor mRNA on vGLUT2 and vGAT neurons within the PPN and CnF. Overall, D2+5R were the highest expressing subtypes of DARs, while D1,3, and 4R were sparsely expressed. There were no significant differences in D1-5R expression between the PPN and CnF. D5R cells showed colocalization with cells expressing vGLUT2 mRNA, while D2R had significant subpopulations of cells expressing both vGAT and vGLUT2 mRNA. My thesis suggests that DA modulation of MLR neurons are predominantly D2R mediated, and dopamine may play a role in opposing behaviours, due to D2R expression on glutamatergic and GABAergic cells. Further investigation is needed to determine the functional role of dopamine receptors in the MLR and upstream nuclei (A13, SNc, or both) contributing to dopaminergic modulation of the MLR.
- ItemOpen AccessThe Effects of High Sucrose or High Fat Diet on Brain Macrostructure, Cognition, and Expression of Phosphorylated Tau(2016) Mackie, Yasmine Olga; Borgland, StephanieConsumption of sucrose-rich and fat-rich foods poses an in increased risk of obesity, and has been shown to be associated with cognitive decline, reduced cortical volume, and dementia. The goal of this thesis was to determine the effect of diet on metabolic measures, gut microbiota, brain macrostructure, cognitive function, and dementia biomarker expression in middle-aged female mice. In Chapter 2, high sucrose diet exposure did not alter metabolism, but increased liver triglyceride concentration and altered gut microbiota relative abundance. We also show that sucrose fed mice experienced a significant decrease in the volume of the parietal temporal cortex, and a deficit in cognitive flexibility. In Chapter 3, high fat diet exposure induced significant differences in weight, glucose sensitivity and plasma leptin levels, without altering the expressions of phosphorylated tau. Together, these studies demonstrate that diet, without affecting metabolic measures, can alter cortical volume and cognitive function.
- ItemEmbargoThe location and functional role for the K+-dependent Na+/Ca2+-exchanger, subtype 4 (NCKX4), in mouse brain(2024-04-18) Hassan, Mohamed Tarek Ahmed; Lytton, Jonathan; Schnetkamp, Paul; Borgland, StephanieThe K+-dependent Na+/Ca2+ exchanger (NCKX) family has emerged as a major regulator of Ca2+ homeostasis. The family comprises five members (NCKX1-5) that are involved in various neuronal functions. In this thesis, I focus on the fourth member (NCKX4) in the brain. While gene expression analysis and immunoblotting of brain lysates demonstrated high expression of NCKX4 in the brain, the regional distribution of the protein product across the brain is unknown. In Chapter 2, I map the expression of NCKX4 throughout the mouse brain. My data reveal that NCKX4 demonstrates distinct and intense expression in multiple areas involved in crucial functions such as learning and memory, reward processing, movement, and cerebrospinal fluid production. Of interest, NCKX4 expression in the choroid plexus epithelial cells (CPECs) exhibited unexpected intracellular distribution. In Chapter 3, I investigate how NCKX4 contributes to the normal function of CPECs by examining the intracellular structure at which NCKX4 is located and changes induced in Nckx4–/– mice, such as CPEC morphology, CSF composition and secretion, and CPEC subcellular Ca2+ dynamics. My data suggest that NCKX4 is partially localized with markers associated with acidic compartments like endo/lysosomal and secretory vesicles, and loss of NCKX4 may lead to alterations in CSF protein composition. However, no changes in CPEC morphology, CSF ionic concentrations, lateral ventricles volume, or Ca2+ activity were found in Nckx4–/– mice. Finally, based on previous reports that link NCKX4 to Alzheimer’s disease and my data (Chapter 2) that show high expression of NCKX4 in hippocampal mossy fibers, in Chapter 4 I investigate the involvement of NCKX4 in learning and memory through a battery of behavioural experiments. Nckx4–/– mice demonstrate deficits in contextual memory formation and recall as well as less anxiety when placed in an open field. No difference was found in the performance of Nckx4–/– mice in novel object recognition task or Barnes maze compared to wildtype controls. The data presented in this thesis provide an expression map in the brain, with an unexpected subcellular location within CPECs, and reveal undiscovered roles for NCKX4 in neuronal function. Many of these results warrant further investigation.
- ItemOpen AccessThe Role of Orexin in Modulating Locomotion(2016) Biswabharati, Sukanya; Whelan, Patrick; Bains, Jaideep; Borgland, Stephanie; Wildering, Willem CarelThe neuropeptides, orexin A/ B, are produced in the lateral hypothalamic region of the brain and are widely released in the central nervous system including locomotor regions in the brainstem and the lumbar spinal cord. Multiple lines of evidence implicate orexin as being capable of influencing locomotion. However, the direct role of orexin in modulating locomotion is not known. Motor networks, which produce rhythmic patterns of activity for locomotion in the hindlimbs reside primarily in the lumbar spinal cord. My work addressed whether direct orexinergic modulation of spinal circuits can affect locomotor behavior. Data, obtained from neurogram recordings of isolated spinal cord preparations, show that application of orexin can powerfully affect the frequency of the locomotor rhythm. Additionally, experiments performed to delineate the effect of orexin onto isolated networks of the motoneurons showed a considerable increase in the firing rate of motoneurons, further suggesting orexin’s involvement in the locomotor circuitry.