Baroreflex responses to electrical stimulation of aortic depressor nerve in conscious SHR

Helio C Salgado; Alvaro R Barale; Jaci A Castania; Benedito H Machado; Mark W Chapleau; Rubens Fazan Jr

doi:10.1152/ajpheart.00181.2006

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Baroreflex responses to electrical stimulation of aortic depressor nerve in conscious SHR

Journal article

Peer reviewed

Baroreflex responses to electrical stimulation of aortic depressor nerve in conscious SHR

Helio C Salgado, Alvaro R Barale, Jaci A Castania, Benedito H Machado, Mark W Chapleau and Rubens Fazan Jr

American journal of physiology. Heart and circulatory physiology, Vol.292(1), pp.H593-600

01/2007

DOI: 10.1152/ajpheart.00181.2006

PMID: 16951050

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Abstract

Baroreflex responses to changes in arterial pressure are impaired in spontaneously hypertensive rats (SHR). Mean arterial pressure (MAP), heart rate (HR), and regional vascular resistances were measured before and during electrical stimulation (5-90 Hz) of the left aortic depressor nerve (ADN) in conscious SHR and normotensive control rats (NCR). The protocol was repeated after beta-adrenergic-receptor blockade with atenolol. SHR exhibited higher basal MAP (150 +/- 5 vs. 103 +/- 2 mmHg) and HR (393 +/- 9 vs. 360 +/- 5 beats/min). The frequency-dependent hypotensive response to ADN stimulation was preserved or enhanced in SHR. The greater absolute fall in MAP at higher frequencies (-68 +/- 5 vs. -38 +/- 3 mmHg at 90-Hz stimulation) in SHR was associated with a preferential decrease in hindquarter (-43 +/- 5%) vs. mesenteric (-27 +/- 3%) resistance. In contrast, ADN stimulation decreased hindquarter and mesenteric resistances equivalently in NCR (-33 +/- 7% and -30 +/- 7%). Reflex bradycardia was also preserved in SHR, although its mechanism differed. Atenolol attenuated the bradycardia in SHR (-88 +/- 14 vs. -129 +/- 18 beats/min at 90-Hz stimulation) but did not alter the bradycardia in NCR (-116 +/- 16 vs. -133 +/- 13 beats/min). The residual bradycardia under atenolol (parasympathetic component) was reduced in SHR. MAP and HR responses to ADN stimulation were also preserved or enhanced in SHR vs. NCR after deafferentation of carotid sinuses and contralateral right ADN. The results demonstrate distinct differences in central baroreflex control in conscious SHR vs. NCR. Inhibition of cardiac sympathetic tone maintains reflex bradycardia during ADN stimulation in SHR despite impaired parasympathetic activation, and depressor responses to ADN stimulation are equivalent or even greater in SHR due to augmented hindquarter vasodilation.

Blood Pressure

Rats, Inbred SHR

Heart Rate

Vascular Resistance

Consciousness

Rats

Male

Treatment Outcome

Hypertension - physiopathology

Animals

Electric Stimulation Therapy - methods

Baroreflex

Aorta - innervation

Aorta - physiopathology

Hypertension - therapy

Electric Stimulation - methods

Details

Title: Subtitle: Baroreflex responses to electrical stimulation of aortic depressor nerve in conscious SHR
Creators: Helio C Salgado - Dept. of Physiology, School of Medicine of Ribeirão Preto, Univ. of São Paulo, Av. Bandeirantes, 3900, 14049-900 Ribeirão Preto, SP, Brazil. hcsalgad@fmrp.usp.br
Alvaro R Barale
Jaci A Castania
Benedito H Machado
Mark W Chapleau
Rubens Fazan Jr
Resource Type: Journal article
Publication Details: American journal of physiology. Heart and circulatory physiology, Vol.292(1), pp.H593-600
Publisher: United States
DOI: 10.1152/ajpheart.00181.2006
PMID: 16951050
ISSN: 0363-6135
eISSN: 1522-1539
Language: English
Date published: 01/2007
Academic Unit: Molecular Physiology and Biophysics; Cardiovascular Medicine; Fraternal Order of Eagles Diabetes Research Center; Internal Medicine
Record Identifier: 9984025697202771

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