The work presented in this thesis examines the role of cardiac sympathetic signalling in the development and maintenance of hypertension in the spontaneously hypertensive rat (SHR); and the role the norepinephrine re-uptake transporter (NET) plays in the sympathetic phenotype during hypertension. <b>Chapter One</b>: reviews (i) cardiac impairment observed in hypertension, (ii) the mechanisms underlying sympathetic neurotransmission and signal termination, (iii) the structure, function, mechanism of action, and role of the norepinephrine (NE) re-uptake transporter in a number of diseases related to sympathetic dysfunction including hypertension. <b>Chapter Two</b>: comprises a detailed rational for the approach taken to; (i) record NET rate in single isolated cells from major sympathetic ganglia using a novel fluorescent assay (NTUA); (ii) measure norepinephrine release from isolated sympathetic cells using a method of carbon fibre based amperometry; (iii) measure autonomic function on living tissue in-vivo and in-vitro using organ bath and whole animal preparations; (iv) quantification of protein expression and protein levels within single cells and isolated ganglia. <b>Chapter Three</b>: examined the cardiac autonomic phenotype of the young pre-hypertensive SHR. Baseline haemodynamics were comparable between the SHR and age matched WKY controls, apart from in-vivo heart rate which the SHR displayed a small, but significant tachycardia. Release of sympathetic neurotransmitter NE, and the co-transmitter NPY were also elevated in the young SHR compared to WKY even though the SHR showed no elevation in arterial blood pressure at this age. Tyrosine hydroxylase levels were unaltered. ³H-NE release studies also revealed there may be a dysfunction in NET in the SHR at this age, as DMI treatment normalised the difference in ³H-NE overflow between the SHR and WKY. <b>Chapter Four</b>: described an investigation in to the activity of the NE re-uptake transporter between older, SHR with established hypertension and age matched normotensive WKY. A novel fluorescent assay of the monoamine transporter family was used to monitor NET activity within isolated sympathetic cells from three ganglia associated with hypertension. Direct evidence for the first time is reported that NET activity was lower in cardiac stellate neurons of the SHR compared to the WKY, but not in the other ganglia tested (superior cervical ganglion (SCG) – vascular innervation of head and neck, and celiac/superior mesenteric ganglia (CG/SMG)– renal and abdominal organs). The data support the notion that NET is regulated in a site-specific fashion, which may account for the sympathetic heterogeneity of NE spillover reported in humans. <b>Chapter Five</b>: examined differences in NET activity and expression levels between four-week-old pre-hypertensive SHR and age matched WKY. The NTUA assay revealed a significantly lower rate of NET activity within stellate neurons of the young SHR compared to WKY, with no difference in NET protein expression. No difference again was seen in the other ganglia. The SCG was the only ganglia in which NET significantly decreased with age, indicating the NET dysregulation within the vasculature may develop at a later stage of hypertension than observed in cardiac ganglia. <b>Chapter Six</b>: examined the ability to modulate NET activity in WKY and SHR stellate neurons in response to a number of pharmacological agents that stimulate cGMP (BNP, SNP, 8-Br-cGMP) and inhibition of PKC. These were agents previously implicated in NET modulation in other cell types. All activators of cGMP reduced NET rate to a similar degree in the WKY. No change in NET rate was observed in the SHR, indicating that NET modulation either intrinsically, and/or receptor membrane insertion, was faulty in the SHR. PKC inhibition increased NET rate in both groups. <b>Chapter Seven</b>: is a concluding discussion summarising the main findings from this thesis, placing them in to physiological context, and discusses avenues of further research.

No description available.

Although parasympathetic activity (PNS) is the primary driver and sympathetic activity (SNS) is a significant inhibitor of colonic propulsive activity, they are rarely measured, and hence, they almost play no role in diagnosing dysfunction or standard treatments for chronic conditions such as refractory constipation. We aimed to develop methodologies for the assessment of autonomic nervous system (ANS) activity, establish criteria for autonomic dysfunction, and study if stimulation of lumbar and sacral autonomic nerves using low-level laser therapy (LLLT) could affect the ANS and explore it as a potential treatment of autonomic dysfunction to restore colonic motility. By studying the active standing test and the table tilt test as a method to evoke activity in the ANS, we rejected LF power, SD1 and SD2 of Poincare plot, Pre-ejection-period (PEP), complex-correlation-measure (CCM) and detrended fluctuation analysis (DFA). Respiratory-Sinus-Arrhythmia (RSA), Root-Mean-Square-of-Successive-Differences (RMSSD) were selected for PNS activity, the Baevsky’s-Stress-Index (SI) was chosen for SNS activity, and SI/RSA and SI/RMSSD were introduced as a measure of autonomic balance. We explored high-resolution-colonic-manometry with concurrent electrocardiography to observe whether these parameters could be associated with ANS changes during colonic motor patterns. High-amplitude-propagating-pressure-waves were associated with a strong parasympathetic activity and decreased sympathetic activity. Comparing ANS reactivity of patients with severe motility disorders to controls in response to postural changes, we observed that most patients have low PNS and elevated SNS baseline activity and reactivity. This established a way to evaluate autonomic dysfunction in patients with colon motor disorders. A single session of LLLT using LED and laser light on the lumbar and sacral spine in 41 patients with chronic gastrointestinal motor dysfunction indicated that treatments with LED light followed by laser light significantly increased parasympathetic activity and decreased sympathetic nervous system activities. These results initiated a study into the effects of LLLT on restoring autonomic dysfunction in chronic refractory colonic motility disorders. / Thesis / Doctor of Philosophy (PhD)

Anxiety is marked by impaired inhibition of distraction (Eysenck et al., 2007). It is unclear whether these impairments are reduced or exacerbated when loading working memory (WM) with non-affective information. Cardiac vagal control has been related to emotion regulation and may serve as a proxy for load-related inhibition under anxiety (Thayer and Lane, 2009). The present study examined whether: (1) the enhancing and impairing effects of load on inhibition exist together in a nonlinear function, (2) there is a similar association between inhibition and concurrent vagal control, (3) nonlinear relations depend on trait anxiety. During anxiogenic threat-of-noise, 116 subjects maintained a digit series of varying lengths (0, 2, 4, 6 digits) while completing a visual flanker task. The task was broken into four blocks, with a baseline period preceding each. ECG was acquired throughout to quantify vagal control as high-frequency heart rate variability (HRV). There were significant quadratic relations of WM load to flanker performance and to HRV, but no associations between HRV and performance. Trait anxiety did not moderate any relations among HRV, load, and inhibition. Results indicate that low load was associated with relatively better inhibition and increased HRV. Findings suggest that attentional performance under anxiety depends on the availability of WM resources, which might be reflected by vagal control. These results have implications for treating anxiety disorders, in which emotion regulation can be optimized for attentional focus. / Ph. D.

published_or_final_version / Pharmacology / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Biochemistry / Doctoral / Doctor of Philosophy

No description available.

This thesis examined Autonomic Nervous System activity evoked by postural instability. Autonomic reactions were assessed using measures of electrodermal activity at the surface of the skin. Perturbation-evoked electrodermal responses (EDRs) were consistently observed in conjunction with both upper and lower limb postural reactions. These autonomic responses were sensitive to perturbation amplitude, as well as experimental manipulations which did not influence the perturbation itself but which affected response execution. In particular, stimulus predictability and movement challenge modulated EDRs, although purely cognitive manipulations did not significantly affect autonomic responses. Probes examining the potential role of such autonomic potentials in compensatory balance control revealed that EDRs evoked during compensatory postural reactions were larger and more consistent than potentials evoked by purely motor or sensory stimuli, suggesting that evoked autonomic activity plays a role in compensatory behavior. While the specific role of autonomic contributions in compensatory balance control require further study, speculative models for autonomic contributions propose either feedback-based pathways for detection of instability to initiate the postural reaction, and/ or an adaptive role to higher centers important for establishing sensorimotor gain in future conditions. This thesis presents new evidence regarding basic neural mechanisms engaged in the recognition and response to postural instability, and future work may extend these findings in clinical populations with high fall incidence and offer clues as to alternative causes for falls and fall prevention.

"Diabetic cardiovascular autonomic neuropathy (DCAN) is common in patients with diabetes mellitus, and causes abnormalities in heart rate control as well as central and peripheral nervous system dynamics. A good understanding of DCAN is not established yet. An effective way to detect diabetes mellitus at an early stage is still undiscovered, which method is highly desired by researchers and patients. One reason why the pathogenesis of DCAN is unclear is that non- invasive assessment of DCAN in humans and animals has been problematic. The non-stationary and non- linear natures of the interested physiological signals have placed great limitation on traditionally algorithms. To overcome this limitation, this work proposes a series of time- varying, nonlinear and non-invasive methods to assess cardiac autonomic dysregulation from ECG and PPG records. Including a non-stationary method called PDM, which is based on principal dynamic mode (PDM) analysis of heart rate variability (HRV), nonstationary power spectral density called TVOPS-VFCDM and also standard spectrum analysis method of HRV. We are also able to study and analyze a series of long term and short term ECG and PPG data. In a pilot study, ECG was measured via telemetry in conscious 4 month old C57/Bl6 controls and in Akita mice, a model of insulin- dependent type I diabetes, while PPG was measured via tail pulse oximetry system from 2 month old to 4 month old. The results indicate significant cardiac autonomic impairment in the diabetic mice in comparison to the controls at 4 month old and such impairment start to present at 3 month old. Further, both immunohistochemistry and Western blot analyses show a reduction in nerve density in Akita mice as compared to the control mice, thus, corroborating our data analysis records."

nÃo hà / IntroduÃÃo: Sarcopenia, estado inflamaÃÃo crÃnica e diminuiÃÃo da modulaÃÃo autonÃmica cardÃaca sÃo frequentemente descritos em idosos frÃgeis. No entanto, o papel da inflamaÃÃo e diminuiÃÃo da modulaÃÃo autonÃmica em perda de massa muscular associada ao envelhecimento deve ser esclarecido. Objetivo: identificar, em idosos frÃgeis e robustos residentes na comunidade, correlaÃÃes entre alteraÃÃes autonÃmicas, nÃveis sÃricos de marcadores bioquÃmicos de inflamaÃÃo e diminuiÃÃo da forÃa e do desempenho muscular. Resultados: 98 voluntÃrios frÃgeis e robustos com idade de 60 anos ou mais foram submetidos à avaliaÃÃo clÃnica, exames laboratoriais e anÃlise da variabilidade da frequÃncia cardÃaca em decÃbito dorsal e em ortostase. O logaritmo natural do Ãndice de variabilidade da frequÃncia cardÃaca baixa frequÃncia (LF) foi inversamente relacionado com o marcador bioquÃmico da inflamaÃÃo fibrinogÃnio em idosos com fragilidade (p=0,046), mas nÃo em robustos. NÃo houve associaÃÃo entre Ãndices de variabilidade da frequÃncia cardÃaca e marcadores bioquÃmicos de inflamaÃÃo interleucina-6 e proteÃna C reativa ultrassensÃvel. Velocidade da marcha foi negativamente relacionada com o fibrinogÃnio em idosos frÃgeis (p=0,033), mas nÃo em idosos robustos. Em todos os idosos, velocidade da marcha foi negativamente relacionada com o fibrinogÃnio (p=0,017), interleucina-6 (p=0,038) e proteÃna C reativa ultrassensÃvel (p=0,010). ConclusÃo: nossos resultados sugerem que a sarcopenia relacionada inflamaÃÃo pode ser, pelo menos parcialmente, influenciada por diminuiÃÃo da modulaÃÃo autonÃmica em idosos. / Background: sarcopenia, chronic inflammation status and impairment of cardiac autonomic modulation are often described in frailty elderly. However, the role of inflammation and decreased autonomic modulation in loss of muscle mass associated with aging need to be enlightened. Aim: we aimed to identify, in community-dwelling frailty and robust elderly, correlations among autonomic changes, serum levels of biochemical markers of inflammation and decreased muscle strength and performance. Results: 98 volunteers aged 60 or older was assessed by clinical evaluation, laboratory tests and analysis of heart rate variability (HRV) in the supine and standing positions. The natural logarithm of the HRV index Low Frequency (LF) was inversely related with the biochemical marker of inflammation fibrinogen in frail elderly (p=0.049), but not in robust. There was no association between heart rate variability indices and biochemical markers of inflammation interleukin-6 and C-reactive protein high sensitivity. Gait speed was negatively correlated with fibrinogen in frail elderly (p=0.033), but not in elderly robust. In all elderly, gait speed correlated negatively with fibrinogen (p=0.017), IL-6 (p=0.038) and high-sensitivity CRP (p=0.010). Conclusion: our results suggest that inflammation-related sarcopenia can be at least partially influenced by decreased autonomic modulation in the elderly.