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ACTIVATION OF PERIPHERAL CHEMORECEPTORS CAUSES POSITIVE INOTROPIC EFFECTS IN A WORKING HEART–BRAINSTEM PREPARATION OF THE RAT
Author(s) -
Braga Valdir A,
Zoccal Daniel B,
Soriano Renato N,
Antunes Vagner R,
Paton Julian F,
Machado Benedito H,
Nalivaiko Eugene
Publication year - 2007
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.2007.04699.x
Subject(s) - inotrope , brainstem , peripheral , chemoreceptor , peripheral chemoreceptors , medicine , cardiology , chemistry , endocrinology , neuroscience , anesthesia , biology , receptor
SUMMARY1 The aim of the present study was to evaluate the effects of peripheral chemoreceptor activation on myocardial contractility in an anaesthetic‐free decerebrated rat preparation. 2 In the decerebrated and retrogradely perfused working heart–brainstem preparation, we recorded phrenic nerve activity, left ventricular (LV) pressure (microtip Millar catheter), LV dP/dT, heart rate and aortic perfusion pressure before and after activating peripheral chemoreceptors with bolus intra‐arterial injections of KCN. 3 Without cardiac pacing, chemoreflex activation caused falls in heart rate (–108 ± 21 b.p.m.) and complex polyphasic changes in LV pressure and LV dP/dT. If the heart was paced, chemoreflex activation caused significant rises in LP pressure (+16 ± 3 mmHg) and LV dP/dt (+778 ± 93 mmHg/s). These positive inotropic effects were significantly and substantially attenuated by β‐adrenoceptor blockade with atenolol. In all instances, chemoreflex activation elicited potent tachypnoeic responses. 4 In conclusion, activation of peripheral chemoreceptors in non‐anaesthetized rats evokes a positive inotropic response that is sympathetically mediated. This observation may be relevant for the evaluation of neurally induced effects of acute hypoxia on the ventricular myocardium.