Central oxytocin modulation of acute stress-induced cardiovascular responses after myocardial infarction in the rat

Abstract

The present study was aimed at determining the role of centrally released oxytocin in regulation of blood pressure and heart rate (HR) under resting conditions and during an acute air-jet stress in rats with a myocardial infarction and controls infarcted. Four weeks after ligation of a coronary artery or sham surgery, conscious Sprague Dawley rats were subjected to one of the following intracerebroventricular (ICV) infusions: (1) 0.9% NaCl (control), (2) oxytocin, (3) oxytocin receptor antagonist {desGly-NH₂-d(CH₂)₅[D-Tyr₂Thr⁴]OVT}(OXYANT). Resting arterial blood pressure and HR were not affected by any of the ICV infusions either in the infarcted or sham-operated rats. In the control experiments, the pressor and tachycardic responses to the air jet of infarcted rats were significantly greater than in the sham-operated rats. OXYANT significantly enhanced the cardiovascular responses to stress only in the sham-operated rats whereas oxytocin significantly attenuated both responses in the infarcted but not in the sham-operated rats. The results suggest that centrally released endogenous oxytocin significantly reduces the cardiovascular responses to the acute stressor in control rats. This buffering function of the brain-oxytocin system is not efficient during the post-myocardial infarction state, however it may be restored by central administration of exogenous oxytocin.

Keywords::

• Heart failure
• myocardial infarct
• neuropeptides
• oxytocin-antagonist
• stress
• vasopressin

Acknowledgements

The authors wish to express their gratitude to Professor Maurice Manning from the Department of Biochemistry and Molecular Biology, Medical College of Ohio, Toledo, USA for the generous supply of oxytocin antagonist used in the present study, to Marzanna Tkaczyk for her skilful technical assistance, and to Marcin Kumosa for preparation of illustrations. This study was supported by a grant from the Medical University of Warsaw (1MAW2/2006-2008).

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.