Short and long term analysis of heart rate variations in spontaneously hypertensive rats: effects of DSP-4 administration.
The purpose of this study was to investigate whether or not central noradrenergic neurons were involved in the time structure of circadian variation of heart rate (HR) in hypertension. We used spontaneously hypertensive rats (SHR(Izm)) and normotensive controls (Wistar Kyoto rats, WKY(Izm)). We selectively destroyed the noradrenergic neurons in the central nervous system (CNS) by administering noradrenergic neurotoxin, N-(2-chloroethy)-N-ethyl-2-bromobenzylamine (DSP4). Frequency domain measures of variation of HR (VHR) were obtained using the maximum entropy method. The 24-h time frame in VHR is usually dominant in both SHR(Izm) and WKY(Izm). Fourteen days after the administering of DSP4, the mean 24-h systolic arterial pressure (SAP) remained higher in SHR(Izm) than in WKY(Izm). After chemical lesion, ultradian rhythms (12-, 8-, 6-, and 4-h periods) in VHR became more remarkable in both SHR(Izm) and WKY(Izm) than before chemical lesion. Before chemical lesion, an inverse relationship existed between frequency and power spectral density in VHR, demonstrating 1/f(beta) characteristics. The slope of 1/f(beta) in VHR did not differ between SHR(Izm) and WKY(Izm). After the chemical lesion it did not also differ from that of each strain in control period (before lesion). Therefore, the noradrenergic neurons may not affect the time structure of HR in SHR(Izm) and WKY(Izm) for short-term time analysis. However, the intact noradrenergic neurons in CNS may be important to keep normal cardiac autonomic function in SHR(Izm) for long-term analysis.
Kawamura
H
H
Department of Medicine, Nippon Dental University School of Dentistry, 2-3-16 Fujimi, Chiyoda-ku, Tokyo 102-8158, Japan. kawamura@tokyo.ndu.ac.jp
Mitsubayashi
H
H
Miao
T
T
Shimizu
T
T
D000818:Animals; D001596:Benzylamines / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002490:Central Nervous System / Q000502:physiology; D006339:Heart Rate / Q000502:physiology*; D006973:Hypertension / Q000188:drug therapy* / Q000503:physiopathology*; D008297:Male; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000502:physiology; D014179:Neurotransmitter Uptake Inhibitors / Q000494:pharmacology*; D009638:Norepinephrine / Q000502:physiology; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D013686:Telemetry
D001596:Benzylamines; D014179:Neurotransmitter Uptake Inhibitors; C012102:DSP 4; D009638:Norepinephrine