title: Asymmetry in the control of cardiac performance by dorsomedial hypothalamus.
abstract: Dorsomedial hypothalamus (DMH) plays a key role in integrating cardiovascular responses to stress. We have recently reported greater heart rate responses following disinhibition of the right side of the DMH (R-DMH) in anesthetized rats and greater suppression of stress-induced tachycardia following inhibition of the R-DMH in conscious rats [both compared with similar intervention in the left DMH (L-DMH)], suggesting existence of right/left side asymmetry in controlling cardiac chronotropic responses by the DMH. The aim of the present study was to determine whether similar asymmetry is present for controlling cardiac contractility. In anesthetized rats, microinjections of the GABAA antagonist bicuculline methiodide (BMI; 40 pmol/100 nl) into the DMH-evoked increases in heart rate (HR), left ventricular pressure (LVP), myocardial contractility (LVdP/dt), arterial pressure, and respiratory rate. DMH disinhibition also precipitated multiple ventricular and supraventricular ectopic beats. DMH-induced increases in HR, LVP, LVdP/dt, and in the number of ectopic beats dependent on the side of stimulation, with R-DMH provoking larger responses. In contrast, pressor and respiratory responses did not depend on the side of stimulation. Newly described DMH-induced inotropic responses were rate-, preload- and (largely) afterload-independent; they were mediated by sympathetic cardiac pathway, as revealed by their sensitivity to β-adrenergic blockade. We conclude that recruitment of DMH neurons causes sympathetically mediated positive chronotropic and inotropic effects, and that there is an asymmetry, at the level of the DMH, in the potency to elicit these effects, with R-DMH > L-DMH.
authors: Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors: Carlos Henrique
authors: CH
authors: Xavier
authors: Mirza Irfan
authors: MI
authors: Beig
authors: Danielle
authors: D
authors: Ianzer
authors: Marco Antônio Peliky
authors: MA
authors: Fontes
authors: Eugene
authors: E
authors: Nalivaiko
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000503:physiopathology; D001640:Bicuculline / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D002304:Cardiac Pacing, Artificial; D004302:Dorsomedial Hypothalamic Nucleus / Q000187:drug effects / Q000502:physiology*; D004562:Electrocardiography; D007839:Functional Laterality / Q000187:drug effects / Q000502:physiology; D058787:GABA-A Receptor Antagonists / Q000494:pharmacology; D006321:Heart / Q000187:drug effects / Q000294:innervation* / Q000502:physiology*; D008297:Male; D008845:Microinjections; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D056152:Respiratory Rate / Q000187:drug effects; D013564:Sympathetic Nervous System / Q000502:physiology; D016277:Ventricular Function, Left / Q000187:drug effects / Q000502:physiology
chemical_list: D000319:Adrenergic beta-Antagonists; D058787:GABA-A Receptor Antagonists; D001640:Bicuculline