title: Ventilatory long-term facilitation is greater in 1- vs. 2-mo-old awake rats.
abstract: Respiratory long-term facilitation (LTF) declines in middle-aged vs. adult male rats. Chronic intermittent hypoxia (CIH; 5 min 11-12% O2/5 min air, 12 h/night, 7 nights) enhances LTF in adult rats. However, LTF in immature rats and the effect of early CIH are unevaluated. The present study compared LTF in 1- and 2-mo-old rats and examined the effect of neonatal CIH (initiated at 2 days after birth) on the LTF. Ventilatory LTF, elicited by 5 (protocol 1) or 10 (protocol 2) episodes of poikilocapnic hypoxia (5 min 12% O2/5 min air), was measured twice by plethysmography on the same male conscious rat when it was 1 and 2 mo old. In untreated (without CIH) rats, both resting ventilation (54.7 +/- 0.6 vs. 43.0 +/- 0.2 ml.100 g(-1).min(-1)) and hypoxic ventilatory response (131 +/- 4 vs. 66 +/- 3% above baseline) were greater in 1- vs. 2-mo-old rats. Protocol 1 elicited LTF in 1-mo-old (12.5 +/- 1.0% above baseline) but not 2-mo-old rats. Protocol 2 elicited a greater LTF in 1-mo-old (24.3 +/- 0.8%) vs. 2-mo-old rats (18.2 +/- 0.5%). In CIH-treated rats, protocol 1 also elicited LTF in 1-mo-old (13.1 +/- 1.5%) but not 2-mo-old rats. Protocol 2 elicited LTF in both age groups, but LTF was enhanced by the CIH only in 1-mo-old rats (28.8 +/- 0.9%). These results suggest that ventilatory LTF and hypoxic ventilatory response are greater in male rats shortly before their sexual maturity and that the neonatal CIH somewhat enhances ventilatory LTF approximately 3 wk after CIH, but this enhancement does not last to adulthood.
authors.affiliation: Div. of Sleep Medicine at BIDMC, Brigham and Women's Hospital, 75 Francis St., Boston, MA 02115, USA.
authors.forename: Michelle
authors.initials: M
authors.lastname: McGuire
authors.forename: Liming
authors.initials: L
authors.lastname: Ling
mesh_terms: D000222:Adaptation, Physiological; D000375:Aging; D000818:Animals; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption; D012123:Pulmonary Ventilation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D014851:Wakefulness
chemical_list: D010100:Oxygen