Premium
EFFECTS OF NORMOXIC AND HYPOXIC BREATHING ON TISSUE PO2 IN THE HYPOTHALAMIC PVN: IMPLICATIONS FOR HYPOXIC ACTIVATION OF SYMPATHETIC NERVE ACTIVITY (SNA).
Author(s) -
Chen QingHui,
Andrade Mary A,
Calderon Alfredo S,
Mifflin Steven W,
Toney Glenn M
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.960.15
Subject(s) - hypoxia (environmental) , chemistry , chemoreceptor , medicine , endocrinology , in vivo , ventilation (architecture) , respiration , breathing , hypoxic hypoxia , anesthesia , respiratory system , oxygen , anatomy , biology , receptor , mechanical engineering , microbiology and biotechnology , organic chemistry , engineering
Carbon fiber electrodes were implanted (3–14 days) in the PVN of rats (n=4) for amperometric recording of tissue pO2. Conscious rats were then placed in a plexiglass chamber and ambient pO2 was varied from normoxic (21%) to hypoxic (10%) levels every 3 minutes. Tissue pO2 averaged 13 ± 2 mmHg in the PVN during normoxic breathing and fell to 3 ± 1 mmHg during hypoxic breathing, during which an increase of renal SNA was observed. The same rats were then anesthetized and identical cycles of normoxic/hypoxic ventilation were performed and produced nearly identical changes of PVN tissue pO2. Effects of physiological variations of tissue pO2 on the activity of RVLM‐projecting pre‐sympathetic PVN neurons were investigated in brain slices. Slices were perfused with aCSF gassed (O2/N2/5%CO2 mixtures) to produce the same levels of tissue pO2 recorded in the PVN in vivo . In whole‐cell voltage‐clamp recordings (Vhold: −80 mV), tissue hypoxia caused an inward shift of holding current (17 ± 3 pA, n=4). Identical experiments in rats exposed to intermittent hypoxia for 7 days, showed that tissue hypoxia induced larger inward shifts of holding current (37 ± 4 pA, n=4). We conclude that tissue pO2 in the PVN varies in phase with normoxic and hypoxic breathing/ventilation and that the level of tissue hypoxia occurring in the PVN in vivo is sufficient to acutely activate currents capable of exciting sympathetic‐regulatory PVN neurons. Support: HL086804 (SWM), HL071645 (GMT)