title: Autonomic control of the cardiovascular system during acclimatization to high altitude: effects of sildenafil.
abstract: Both acute hypoxia and sildenafil may influence autonomic control through transient cardiovascular effects. In a double-blind study, we investigated whether sildenalfil (Sil) could interfere with cardiovascular effects of hypoxia. Twelve healthy men [placebo (Pla) n = 6; Sil, n = 6] were exposed to an altitude of 4,350 m during 6 days. Treatment was continuously administered from 6 to 8 h after arrival at altitude (3 x 40 mg/day). The autonomic control on the heart was assessed by heart rate variability (HRV) during sleep at sea level (SL) and between day 1-2 and day 5-6 in hypoxia. Arterial pressure (AP) and total peripheral resistances (TPR) were obtained during daytime. There was no statistical difference between groups in HRV, AP, and TPR throughout the study. Hypoxia induced a decrease in R-R interval and an increase in AP in both groups. Low frequency-to-high frequency ratio increased at day 1-2 (Pla, P = 0.04; Sil, P = 0.02) and day 5-6 (Pla and Sil, P = 0.04) vs. SL, whereas normalized high-frequency power decreased only in Pla (P = 0.04, day 1-2 vs. SL). Normalized low-frequency power increased at high altitude (Pla and Sil, P = 0.04, day 5-6 vs. SL). TPR decreased at day 2 in Pla (P = 0.02) and tended to normalize at day 6 (P = 0.07, day 6 vs. day 2). Acute hypoxia induced a decrease in parasympathetic and increase in sympathetic tone, which tended to be reversed with acclimatization. Sil had no deleterious effects on the cardiovascular response to high-altitude exposure and its control by the autonomic nervous system.
authors.affiliation: Laboratoire Réponses Cellulaires et Fonctionnelles à l'Hypoxie, Université Paris 13, 93017 Bobigny, France.
authors.forename: Jérémy
authors.initials: J
authors.lastname: Cornolo
authors.forename: Pascal
authors.initials: P
authors.lastname: Mollard
authors.forename: Julien V
authors.initials: JV
authors.lastname: Brugniaux
authors.forename: Paul
authors.initials: P
authors.lastname: Robach
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Richalet
mesh_terms: D000064:Acclimatization / Q000187:drug effects; D000328:Adult; D000532:Altitude Sickness / Q000503:physiopathology*; D001341:Autonomic Nervous System / Q000187:drug effects* / Q000503:physiopathology*; D001794:Blood Pressure / Q000187:drug effects; D002319:Cardiovascular System / Q000187:drug effects / Q000294:innervation / Q000503:physiopathology; D006321:Heart / Q000187:drug effects / Q000294:innervation* / Q000503:physiopathology*; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology; D008297:Male; D010879:Piperazines / Q000008:administration & dosage*; D011687:Purines; D000068677:Sildenafil Citrate; D013450:Sulfones; D014655:Vascular Resistance / Q000187:drug effects; D014665:Vasodilator Agents / Q000008:administration & dosage
chemical_list: D010879:Piperazines; D011687:Purines; D013450:Sulfones; D014665:Vasodilator Agents; D000068677:Sildenafil Citrate