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Chronic hypoxia induces changes in the central nervous system processing of arterial chemoreceptor input. Adv Exp Med Biol 2000;475:477-84 PMID: 10849688

Pubmed ID

10849688

Abstract

Chronic hypoxia increases the hypoxic ventilatory response (HVR) in awake rats and the phrenic nerve response to carotid sinus nerve stimulation in anesthetized rats. An increased O2 sensitivity of the arterial chemoreceptors contributes to the increase in the HVR, but changes in the CNS processing of afferent information from arterial chemoreceptors are also involved. Adult male Sprague-Dawley rats were exposed to 0-7 days of hypobaric hypoxia (PIO2 = 80 Torr). Ventilation was measured in rats exposed to 0, 2 and 7 days of hypoxia using whole-body plethysmography. Ventilation increased after 2 days and remained elevated after 7 days of hypoxia. Following dopamine D2 receptor (D2-R) blockade in the CNS, frequency significantly decreased after 0 and 7 days of hypoxia, but did not change significantly after 2 days of hypoxia. In anesthetized rats, the phrenic nerve response to carotid sinus nerve stimulation was reduced following systemic D2-R blockade in control rats and those exposed to 7 days of hypoxia. After 2 days of hypoxia, there was no effect of blocking systemic D2-R. To determine whether changes in D2-R mRNA precede physiological changes, competitive RT-PCR was used to quantify D2-R mRNA in micropunches from the nucleus tractus solitarius (NTS) in normoxic and chronically hypoxic rats. In hypoxia, D2-R mRNA in the caudal NTS initially increased (6-12 hours) and then decreased below control levels (24 hours-7 days). These results show that chronic hypoxia causes time-dependent changes in D2-R that could result in changes in the ventilatory response to hypoxia.

Author List

Dwinell MR, Huey KA, Powell FL

Author

Melinda R. Dwinell PhD Center Associate Director, Associate Professor in the Physiology department at Medical College of Wisconsin




Scopus

2-s2.0-0034465921   14 Citations

MESH terms used to index this publication - Major topics in bold

Acclimatization
Animals
Arteries
Carotid Sinus
Central Nervous System
Chemoreceptor Cells
Hypoxia
Male
Phrenic Nerve
RNA, Messenger
Rats
Rats, Sprague-Dawley
Receptors, Dopamine D2
Respiration
Solitary Nucleus
jenkins-FCD Prod-299 9ef562391eceb2b8f95265c767fbba1ce5a52fd6