Clinical autonomic research : official journal of the Clinical Autonomic Research Society
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We previously demonstrated that only men showed a significant correlation between heart rate (HR) and pain. Other authors also found sex differences in the autonomic and cardiovascular reactivity to pain, and sex hormones have been proposed to be partly responsible for these differences. However, no previous studies were done to examine if the autonomic and cardiovascular reactivity to pain vary across the menstrual cycle (MC). ⋯ These results add to our previous finding but tend to show that sex hormones have minimal influence on autonomic reactivity. Moreover, the great variability in intra- and inter-subject reactivity to pain does not allow us to predict the autonomic and cardiovascular reactivity to pain women will show throughout the MC.
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Individuals with tetraplegia have impaired central control of sympathetic vascular modulation and blood pressure (BP); how this impairment affects cerebral blood flow (CBF) is unclear. ⋯ Despite impaired sympathetic vasomotor and BP control, CBF in persons with tetraplegia was comparable to that of control subjects during a hypotensive challenge.
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Neurogenic orthostatic hypotension results from failure to release norepinephrine, the neurotransmitter of sympathetic postganglionic neurons, appropriately upon standing. In double blind, cross over, placebo controlled trials, administration of droxidopa, a synthetic amino acid that is decarboxylated to norepinephrine by the enzyme L: -aromatic amino acid decarboxylase increases standing blood pressure, ameliorates symptoms of orthostatic hypotension and improves standing ability in patients with neurogenic orthostatic hypotension due to degenerative autonomic disorders. The pressor effect results from conversion of droxidopa to norepinephrine outside the central nervous system both in neural and non-neural tissue. This mechanism of action makes droxidopa effective in patients with central and peripheral autonomic disorders.
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Quantitative sensory testing (QST) is a subjective method of assessing thermal sensation, but it does not provide an objective measure of physiological changes. Our aim was to establish whether fluctuations in sudomotor autonomic activity correlate with warmth and heat pain (thermoalgesic) perception. ⋯ In all stimuli paradigms, the mean delay time of the SSR was 1.6 s after the warmth or pain sensation. There was an association between the low amplitude (predominantly negative) SSR and warm stimuli, and the large amplitude (predominantly positive) SSR and heat pain stimuli (chi-square; P < 0.05). Mean EDA was significantly higher during the pain phase in comparison with pre-perception, warmth and post-perception phases. INTEPRETATION: Thermoalgesic stimuli induce reflex changes in sudomotor activity that correlate with subjective perception of warmth and heat pain sensations. This association may be useful in clinical practice.
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Heart rate recovery (HRR) after exercise and spectral decomposition of heart rate variability (HRV), measures of autonomic nervous system function, are predictors of cardiovascular morbidity/mortality. QT interval, an index of ventricular depolarization and repolarization attained from surface ECG, is also associated with morbidity/mortality and is strongly influenced by autonomic tone. The purpose of this study was to assess the association between HRR after exercise, resting HRV and resting rate corrected QT interval in young healthy men. ⋯ There was no correlation between high frequency power of HRV (a marker of parasympathetic modulation) and QTc interval. There was a negative relationship between absolute LF power (a marker of both sympathetic and parasympathetic modulation) and QTc interval for Karjalainen, Framingham, and Bazett correction methods (r = -0.33 to -0.47, P < 0.05). Resting LF power of HRV and HRR after exercise are inversely associated with resting QTc interval in young healthy men, supporting a relationship between cardiac autonomic nervous system function and ventricular depolarization and repolarization.