title: Chronic angiotensin-II treatment potentiates HR slowing in Sprague-Dawley rat during acute behavioral stress.
abstract: This study examined the effect of 2-week infusion of angiotensin-II (Ang-II; 175 ng/kg/min) via minipump in rats (n=7) upon the mean arterial blood pressure (mBP) and heart rate (HR) response to an acute stress as compared to rats infused with saline (n=7). The acute stress was produced by a classical aversive conditioning paradigm: a 15s tone (CS+) followed by a half second tail shock. Baseline mBP in Ang-II infused rats (167.7±21.3 mm Hg; mean±SD) significantly exceeded that of controls (127.6±13.5 mm Hg). Conversely, baseline HR in the Ang-II infused rats (348±33) was significantly lower than controls (384±19 bpm). The magnitude of the mBP increase during CS+ did not differ between groups, but the HR slowing during CS+ in the Ang-II infused rats (-13.2±8.9 bpm) was significantly greater than that seen in controls (-4.2±5.5 bpm). This augmented bradycardia may be inferentially attributed to an accentuated increase in cardiac parasympathetic activity during CS+ in the Ang-II infused rats. The mBP increased above baseline immediately post-shock delivery in controls, but fell in the Ang-II infused rats, perhaps because of a 'ceiling effect' in total vascular resistance. This classical conditioning model of 'acute stress' differs from most stress paradigms in rats in yielding a HR slowing concomitant with a pressor response, and this slowing is potentiated by Ang-II.
authors: Department of Natural Sciences, Asbury College, Wilmore, KY, USA.
authors: Richard E
authors: RE
authors: Hoyt
authors: Richard O
authors: RO
authors: Speakman
authors: David R
authors: DR
authors: Brown
authors: Lisa A
authors: LA
authors: Cassis
authors: Dennis L
authors: DL
authors: Silcox
authors: Chikodi N
authors: CN
authors: Anigbogu
authors: David C
authors: DC
authors: Randall
mesh_terms: D000804:Angiotensin II / Q000008:administration & dosage / Q000009:adverse effects / Q000378:metabolism*; D000818:Animals; D001362:Avoidance Learning; D001522:Behavior, Animal / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D001919:Bradycardia / Q000139:chemically induced / Q000209:etiology* / Q000523:psychology; D002319:Cardiovascular System / Q000187:drug effects / Q000294:innervation* / Q000378:metabolism; D004195:Disease Models, Animal; D004343:Drug Implants; D006339:Heart Rate / Q000187:drug effects; D006973:Hypertension / Q000139:chemically induced / Q000209:etiology / Q000523:psychology; D008297:Male; D010275:Parasympathetic Nervous System / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D013315:Stress, Psychological / Q000378:metabolism / Q000503:physiopathology*
chemical_list: D004343:Drug Implants; D000804:Angiotensin II