title: Reduced respiratory neural activity elicits phrenic motor facilitation.
abstract: We hypothesized that reduced respiratory neural activity elicits compensatory mechanisms of plasticity that enhance respiratory motor output. In urethane-anesthetized and ventilated rats, we reversibly reduced respiratory neural activity for 25-30 min using: hypocapnia (end tidal CO(2)=30 mmHg), isoflurane (~1%) or high frequency ventilation (HFV; ~100 breaths/min). In all cases, increased phrenic burst amplitude was observed following restoration of respiratory neural activity (hypocapnia: 92±22%; isoflurane: 65±22%; HFV: 54±13% baseline), which was significantly greater than time controls receiving the same surgery, but no interruptions in respiratory neural activity (3±5% baseline, p<0.05). Hypocapnia also elicited transient increases in respiratory burst frequency (9±2 versus 1±1bursts/min, p<0.05). Our results suggest that reduced respiratory neural activity elicits a unique form of plasticity in respiratory motor control which we refer to as inactivity-induced phrenic motor facilitation (iPMF). iPMF may prevent catastrophic decreases in respiratory motor output during ventilatory control disorders associated with abnormal respiratory activity.
authors.affiliation: Department of Comparative Biosciences, University of Wisconsin-Madison, 2015 Linden Drive, Madison, WI 53706-1102, USA.
authors.forename: Safraaz
authors.initials: S
authors.lastname: Mahamed
authors.forename: Kristi A
authors.initials: KA
authors.lastname: Strey
authors.forename: Gordon S
authors.initials: GS
authors.lastname: Mitchell
authors.forename: Tracy L
authors.initials: TL
authors.lastname: Baker-Herman
mesh_terms: D000818:Animals; D016857:Hypocapnia / Q000503:physiopathology; D008297:Male; D010791:Phrenic Nerve / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012143:Respiratory Physiological Phenomena