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Differential effects of selective versus nonselective alpha adrenergic receptor blockade on cardiovascular (CV) parameters and heart rate variability (HRV) in rats
Author(s) -
Bhatt Siddhartha,
Northcott Carrie Annalice,
Ringer Laura,
Wisialowski Todd,
Flynn Declan,
SteidlNichols Jill
Publication year - 2013
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.27.1_supplement.926.16
Subject(s) - phentolamine , doxazosin , medicine , heart rate variability , tachycardia , heart rate , endocrinology , propranolol , autonomic nervous system , adrenergic , reflex , chemistry , blood pressure , receptor
HRV analysis is an important noninvasive tool for investigating autonomic nervous system influence on the heart. The objective of the study was to compare CV profiles of doxazosin (selective á1 blocker) at 10 mg/kg, p.o. and phentolamine (non selective á blocker) at 20 and 100 mg/kg. p.o. in conscious rats using telemetry and subsequent HRV analysis, in addition plasma norepinephrine (NE) was also measured. Doxazosin caused a sustained decrease in blood pressure (BP): maximum change −12 mmHg occurred at 8–16 hours post dose (hpd), induced reflex tachycardia (65 bpm) and increased plasma NE levels by 3 fold. HRV analysis revealed no change in high (HF) and low (LF) frequency power compared to vehicle. Phentolamine decreased BP: maximum changes of −9.2 mmHg (20 mg/kg) and −29.1 mmHg (100 mg/kg) occurred at 0–2 hpd with reflex tachycardia (71 and 111 bpm respectively), reduced body temperature and increased NE 10 fold compared to vehicle. HRV analysis revealed a significantly reduced LF/HF ratio with a significant increase in HF but no change in LF at 0–2 hpd. 22 hpd there were no changes in any parameters measured, suggesting the changes observed were treatment‐mediated. It is hypothesized that the increased parasympathetic tone (HF) with phentolamine could be compensatory in response to reflex tachycardia and immediate NE release. In conclusion, doxazosin and phentolamine show differential effects on HRV and CV parameters