Breathing at high altitude.
Acclimatization to long-term hypoxia takes place at high altitude and allows gradual improvement of the ability to tolerate the hypoxic environment. An important component of this process is the hypoxic ventilatory acclimatization (HVA) that develops over several days. HVA reveals profound cellular and neurochemical re-organization occurring both in the peripheral chemoreceptors and in the central nervous system (in brainstem respiratory groups). These changes lead to an enhanced activity of peripheral chemoreceptor and re-inforce the central translation of peripheral inputs to efficient respiratory motor activity under the steady low O(2) pressure. We will review the cellular processes underlying these changes with a particular emphasis on changes of neurotransmitter function and ion channel properties in peripheral chemoreceptors, and present evidence that low O(2) level acts directly on brainstem nuclei to induce cellular changes contributing to maintain a high tonic respiratory drive under chronic hypoxia.
Joseph
Vincent
V
Department of Pediatrics, Laval University, Centre de Recherche (D0-711), Hôpital St-François d'Assise, 10 rue de l'Espinay, Quebec, QC, G1L 3L5, Canada. joseph.vincent@crsfa.ulaval.ca
Pequignot
Jean-Marc
JM
D000531:Altitude; D000818:Animals; D002344:Carotid Body / Q000503:physiopathology; D002490:Central Nervous System / Q000503:physiopathology; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology; D008954:Models, Biological; D010101:Oxygen Consumption / Q000502:physiology; D012119:Respiration