American journal of physiology. Regulatory, integrative and comparative physiology
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Am. J. Physiol. Regul. Integr. Comp. Physiol. · Jun 2003
Cardiac effects of hypocretin-1 in nucleus ambiguus.
Although recent studies have reported hypocretin 1 (hcrt-1)-like-immunoreactivity (ir) within the region of the nucleus ambiguus (Amb) in the caudal brain stem, the function of hcrt-1 in the Amb on cardiovascular function is not known. Three series of experiments were done in male Wistar rats to investigate the effects of microinjections of hcrt-1 into Amb on heart rate (HR), mean arterial pressure (MAP), and the arterial baroreceptor reflex. In the first series, a detailed mapping of the distribution of hcrt-1- and hcrt-1 receptor (hcrtR-1)-like-ir was obtained of the Amb region. ⋯ Administration (iv) of the muscarinic receptor antagonist atropine methyl bromide or ipsilateral vagotomy abolished the HR response, indicating that the HR response was due to activation of vagal cardiomotor neurons. In the final series, microinjections of hcrt-1 into the Ambe significantly potentiated the reflex bradycardia elicited by activation of the baroreflex as a result of the increased MAP after the intravenous injection of phenylephrine. These data suggest that hcrt-1 in the Ambe activates neuronal systems that alter the excitability of central circuits that reflexly control the circulation through the activation of vagal preganglionic cardioinhibitory neurons.
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Am. J. Physiol. Regul. Integr. Comp. Physiol. · Nov 2002
Clinical TrialHeart rate control and mechanical cardiopulmonary coupling to assess central volume: a systems analysis.
Small negative changes of central volume reduce cardiac output without significant alterations of arterial blood pressure (ABP), suggesting an adequate regulatory response. Furthermore, evidence has arisen supporting a Bainbridge reflex (tachycardia with hypervolemia) in humans. To investigate these phenomena, multivariate autoregressive techniques were used to evaluate the beat-to-beat interactions between respiration, R-R interval, and ABP at six levels of decreased and increased central volume. ⋯ The mechanical influence of respiration on central venous pressure (CVP) had an unexpected shift in phase at the point of mild central hypervolemia, with the expected negative relation at lower volumes (inspiration lowers CVP) but a positive relation at higher volumes (inspiration raises CVP). We conclude that multivariate techniques can quantify the relations between a variety of respiratory and hemodynamic parameters, allowing for the in vivo assessment of complex cardiorespiratory interactions during manipulations of central volume. The results identify the presence of a Bainbridge reflex in humans and suggest that short-term cardiovascular control is optimized at mild hypervolemia.
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Am. J. Physiol. Regul. Integr. Comp. Physiol. · Nov 2002
Comparative StudyNovel mechanism for high-altitude adaptation in hemoglobin of the Andean frog Telmatobius peruvianus.
In contrast to birds and mammals, no information appears to be available on the molecular adaptations for O(2) transport in high-altitude ectothermic vertebrates. We investigated Hb of the aquatic Andean frog Telmatobius peruvianus from 3,800-m altitude as regards isoform differentiation, sensitivity to allosteric cofactors, and primary structures of the alpha- and beta-chains, and we carried out comparative O(2)-binding measurements on Hb of lowland Xenopus laevis. ⋯ The data indicate adaptive significance of alpha-chain chloride-binding sites in amphibians, in contrast to human Hb where chloride appears mainly to bind in the cavity between the beta-chains. The findings are discussed in relation to other strategies for high-altitude adaptations in amphibians.
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Am. J. Physiol. Regul. Integr. Comp. Physiol. · Oct 2002
Gene expression analysis in burn wounds of rats.
The events occurring early in the burn wound trigger a sequence of local and systemic responses that influence cell and tissue survival and, consequently, wound healing and recovery. Using high-density oligonucleotide arrays we identified gene expression patterns in skin samples taken from a region of injury in the burn rat model. The associated genomic events include the differential expression of genes involved in cell survival and death, cell growth regulation, cell metabolism, inflammation, and immune response. The functional gene cluster detected and their time appearance matched the time sequence known to occur in burn wound healing.
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Am. J. Physiol. Regul. Integr. Comp. Physiol. · Sep 2002
Increased GABA(A) inhibition of the RVLM after hindlimb unloading in rats.
Attenuated baroreflex-mediated increases in renal sympathetic nerve activity (RSNA) in hindlimb unloaded (HU) rats apparently are due to changes within the central nervous system. We hypothesized that GABA(A) receptor-mediated inhibition of the rostral ventrolateral medulla (RVLM) is increased after hindlimb unloading. Responses to bilateral microinjection of the GABA(A) antagonist (-)-bicuculline methiodide (BIC) into the RVLM were examined before and during caudal ventrolateral medulla (CVLM) inhibition in Inactin-anesthetized control and HU rats. ⋯ These data indicate that GABA(A) receptor-mediated inhibition of RVLM neurons is augmented after hindlimb unloading. Effects of input from the CVLM were unaltered. Thus, after cardiovascular deconditioning in rodents, the attenuated increase in sympathetic nerve activity in response to hypotension is associated with greater GABA(A) receptor-mediated inhibition of RVLM neurons originating at least in part from sources other than the CVLM.