Cardiovascular and sympathetic nervous system responses to an acute stressor in borderline hypertensive rats (BHR).
The present study examined cardiovascular and plasma catecholamine responses to acute footshock stress in adult male Wistar-Kyoto (WKY) normotensive, borderline hypertensive (BHR), and spontaneously hypertensive (SHR) rats. Basal mean arterial pressure and heart rate were equivalent for SHRs and BHRs, and levels for both groups were elevated compared to WKYs. Following transfer to the footshock chamber, blood pressure increased to a greater degree in SHRs than in WKYs or BHRs. However, the tachycardia was exaggerated in both BHRs and SHRs compared to WKYs. In response to intermittent footshock stress, all groups had comparable heart rate increases while maintaining blood pressure near baseline levels. SHRs demonstrated a sympathetic hyperresponsiveness to footshock stress, with greater increases in plasma norepinephrine and epinephrine levels than WKYs immediately following footshock. At 5 minutes postfootshock, plasma catecholamines remained elevated in SHRs over both WKYs and BHRs. Plasma catecholamine increases following footshock were comparable at all time points between WKYs and BHRs. The present results demonstrate that sympathetic responsiveness of BHRs to acute footshock stress is more similar to normotensive WKYs than to hypertensive SHRs.
Kirby
R F
RF
Department of Psychology, University of Iowa, Iowa City 52242.
Callahan
M F
MF
McCarty
R
R
Johnson
A K
AK
D000818:Animals; D001794:Blood Pressure / Q000502:physiology*; D004597:Electroshock; D004837:Epinephrine / Q000097:blood; D006339:Heart Rate / Q000502:physiology*; D008297:Male; D009638:Norepinephrine / Q000097:blood; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D013045:Species Specificity; D013312:Stress, Physiological / Q000097:blood / Q000503:physiopathology*; D013564:Sympathetic Nervous System / Q000502:physiology*
D009638:Norepinephrine; D004837:Epinephrine