Influence of acute progressive hypoxia on cardiovascular variability in conscious spontaneously hypertensive rats.
The purpose of this study is to examine the influence of acute progressive hypoxia on cardiovascular variability and striatal dopamine (DA) levels in conscious, spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY). After preparation for measurement, the inspired oxygen concentration of rats was decreased to 10% within 5 min (descent stage), maintained at 10% for 10 min (fixed stage), and then elevated back to 20% over 5 min (recovery stage). The systolic blood pressure (SBP) and heart rate (HR) variability at each stage was calculated to evaluate the autonomic nervous system response using the wavelet method. Striatal DA during each stage was measured using in vivo microdialysis. We found that SHR showed a more profound hemodynamic response to progressive hypoxia as compared to WKY. Cardiac parasympathetic activity in SHR was significantly inhibited by acute progressive hypoxia during all stages, as shown by the decrease in the high frequency band of HR variability (HR-HF), along with transient increase in sympathetic activity during the early hypoxic phase. This decrease in the HR-HF continued even when SBP was elevated. Striatal DA levels showed the transient similar elevation in both groups. These findings suggest that acute progressive hypoxic stress in SHR inhibits cardiac parasympathetic activity through reduction of baroreceptor reflex sensitivity, with potentially severe deleterious effects on circulation, in particular on HR and circulatory control. Furthermore, it is thought that the influence of acute progressive hypoxia on striatal DA levels is similar in SHR and WKY.
Sugimura
Mitsutaka
M
Department of Dental Anesthesiology, Graduate School of Dentistry, Osaka University, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan. Electronic address: smit@dent.osaka-u.ac.jp.
Hirose
Yohsuke
Y
Department of Dental Anesthesiology, Graduate School of Dentistry, Osaka University, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan.
Hanamoto
Hiroshi
H
Department of Dental Anesthesiology, Graduate School of Dentistry, Osaka University, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan.
Okada
Kenji
K
Department of Dental Anesthesiology, Graduate School of Dentistry, Osaka University, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan.
Boku
Aiji
A
Department of Dental Anesthesiology, Graduate School of Dentistry, Osaka University, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan.
Morimoto
Yoshinari
Y
Department of Dental Anesthesiology, Graduate School of Dentistry, Osaka University, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan.
Taki
Kunitaka
K
Department of Dental Anesthesiology, Graduate School of Dentistry, Osaka University, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan.
Niwa
Hitoshi
H
Department of Dental Anesthesiology, Graduate School of Dentistry, Osaka University, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan.
D000818:Animals; D001479:Basal Ganglia / Q000378:metabolism / Q000503:physiopathology; D001794:Blood Pressure / Q000502:physiology; D002319:Cardiovascular System / Q000503:physiopathology*; D003243:Consciousness / Q000502:physiology*; D004298:Dopamine / Q000032:analysis; D006339:Heart Rate / Q000502:physiology; D006973:Hypertension / Q000503:physiopathology*; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D017551:Microdialysis; D010275:Parasympathetic Nervous System / Q000503:physiopathology; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D013564:Sympathetic Nervous System / Q000503:physiopathology
D004298:Dopamine