Autonomic neuroscience : basic & clinical
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The aim of this study was to determine whether pre-treatment of human skin with the alpha(1)-adrenoceptor antagonist terazosin would block vasoconstrictor responses and axon-reflex vasodilatation to the alpha(1)-adrenoceptor agonist methoxamine. Drugs were administered by iontophoresis into the skin of the forearm of 15 healthy participants, and skin blood flow was monitored with a laser Doppler flow probe at the site of methoxamine iontophoresis (to monitor direct vasoconstrictor responses) or 5-10 mm from the site of methoxamine iontophoresis (to monitor axon-reflex vasodilatation). ⋯ Pre-treatment with terazosin blocked vasoconstrictor responses to increasing doses of methoxamine, and also blocked vasodilatation several mm from the site of terazosin and methoxamine administration. These findings support the view that alpha(1)-adrenoceptors play a role in generating axon-reflex vasodilatation, and thus might contribute to local vascular disturbances in acute and chronic inflammation.
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We examined the Hurst exponent of heart rate time series and its relation with the subjective measures of valence and arousal in two groups of subjects. The electrocardiogram (ECG) and the subjective valence and arousal were measured during the administration of emotional film stimuli (happiness, sadness, anger and fear). The results showed that there is a difference in the Hurst exponent for the happiness and sadness conditions but not between the negative emotion conditions (sadness, anger and fear). This seems to indicate that the Hurst exponent is an indicator of subjective valence.
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The present study has investigated the effect of blockade of nitric oxide synthesis on cardiovascular autonomic adaptations induced by aerobic physical training using different approaches: 1) double blockade with methylatropine and propranolol; 2) systolic arterial pressure (SAP) and heart rate variability (HRV) by means of spectral analysis; and 3) baroreflex sensitivity. ⋯ Our results showed that nitric oxide synthesis blockade impaired the cardiovascular autonomic adaptations induced by previous aerobic physical training in rats that might be, at least in part, ascribed to a decreased baroreflex sensitivity.
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Studies have shown that the dorsomedial hypothalamus (DMH) is a key region in the descending pathways mediating the cardiovascular response to emotional stress. We have recently demonstrated that the lateral/dorsolateral periaqueductal gray (l/dlPAG) is an important synaptic relay in mediating the tachycardic effect produced by activation of DMH neurons. This synaptic relay is mediated via NMDA excitatory amino acid receptors. ⋯ The tachycardic and pressor responses evoked by air jet stress paradigm were also attenuated after treatment with 8-OH-DPAT in the l/dlPAG. The increases in heart rate and arterial pressure produced by microinjection of the excitatory amino acid receptor agonist, NMDA, into the l/dlPAG were largely reduced (by 94% and 73%, respectively) after treatment in the same region with 8-OH-DPAT. Taken together, our findings indicate that 5-HT(1A) receptors at the lateral dorsolateral PAG play a significant role in modulating the descending cardiovascular pathways from the dorsomedial hypothalamus and consequently the cardiovascular response to emotional stress.
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Changes in heart rate variability (HRV) during anesthesia likely result from the interaction of hypnosis, surgical stimulation, analgesia and direct cardiovascular effects of drugs, but the interaction between these variables is unclear. This study was designed to characterize the impact of both surgical nociception and analgesia on HRV in propofol-anesthetized patients. ⋯ The nociception-analgesia balance is a direct determinant of HRV during surgical anesthesia. HFnu may behave like an early indicator of inadequate analgesia. These results have potential implication for monitoring adequacy of analgesia in healthy patients undergoing intravenous anesthesia. Additional work is needed for application across patient populations.