Carotid body function in aged rats: responses to hypoxia,ischemia, dopamine,and adenosine |
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Authors: | Teresa Castro Monteiro Joana Rita Batuca Ana Obeso Constancio González Emília Carreira Monteiro |
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Institution: | 1.Department of Pharmacology, CEDOC/Chronic Diseases Unit, Faculty of Medical Sciences,New University of Lisbon,Lisbon,Portugal;2.Department of Biochemistry, Molecular Biology and Physiology, Faculty of Medicine and IBGM,University of Valladolid,Valladolid,Spain;3.CSIC,CIBER de Enfermedades Respiratorias,Valladolid,Spain;4.Department of Pharmacology, Faculty of Medical Sciences,New University of Lisbon,Lisbon,Portugal |
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Abstract: | The carotid body (CB) is the main arterial chemoreceptor with a low threshold to hypoxia. CB activity is augmented by A2-adenosine receptors stimulation and attenuated by D2-dopamine receptors. The effect of aging on ventilatory responses mediated by the CB to hypoxia, ischemia, and to adenosine
and dopamine administration is almost unknown. This study aims to investigate the ventilatory response to ischemia and to
adenosine, dopamine, and their antagonists in old rats, as well as the effect of hypoxia on adenosine 3′,5′-cyclic monophosphate
(cAMP) accumulation in the aged CB. In vivo experiments were performed on young and aged rats anesthetized with pentobarbitone
and breathing spontaneously. CB ischemia was induced by bilateral common carotid occlusions. cAMP content was measured in
CB incubated with different oxygen concentrations. Hyperoxia caused a decrease in cAMP in the CB at all ages, but no differences
were found between normoxia and hypoxia or between young and old animals. The endogenous dopaminergic inhibitory tonus is
slightly reduced. However, both the ventilation decrease caused by exogenous dopamine and the increase mediated by A2A-adenosine receptors are not impaired in aged animals. The bradycardia induced by adenosine is attenuated in old rats. The
CB’s peripheral control of ventilation is preserved during aging. Concerns have also arisen regarding the clinical usage of
adenosine to revert supraventricular tachycardia and the use of dopamine in critical care situations involving elderly people. |
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Keywords: | Aging Peripheral chemoreceptors Ventilation Domperidone cAMP Adenosine A2A receptors |
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