Contribuição de diferentes sinapses do hipotálamo paraventricular para o controle da função cardíaca
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2017-07-25
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Universidade Federal de Goiás
Resumo
Within the hypothalamic areas involved in the control of cardiovascular function,
neurons of the paraventricular hypothalamus play a key role, either by projecting to the
sympathetic premotor neurons of rostroventrolateral medulla (RVLM) or by reaching
preganglionic neurons of the spinal intermediolateral column (IML). Despite describing the
role of PVH in the cardiovascular control, literature lacks of data on the PVH contribution
to the control of cardiac function. In this regard, the aim of the present study was to assess whether gabaergic and adrenergic synapses, known for being active at the PVH, are
involved in the control of cardiac function by its neurons in normotensive anesthetized
animals. Experiments were performed in adult male Wistar rats (250-350g) that were
anesthetized with urethane (1.2-1.4 g/kg i.p.) and underwent catheterization of femoral to
record arterial pressure and heart rate. Femoral vein was used to inject the vasoactive
drugs phenylephrine (10μg/kg) the sodium nitroprussiate (10μg/kg), the blocker of cardiac
pacemaker zatebradine (1mg/kg) and to supplement anesthesia. The cardiac left ventricle
was catheterized to record the left ventricular pressure and its derivative. Craniotomy
allowed for injections into the PVH of: muscimol (20mM – 100nL), bicuculline (0,4mM -
100nL), propranolol (10mM – 100nL), isoproterenol (100μM – 100nL), fentolamine (13mM
– 100nL), phenylephrine (30nM – 100nL). The main results were: i) inhibition of PVH by
injecting GABAA agonist muscimol, reduced arterial pressure and cardiac inotropy; ii)
disihibition of PVH neurons by injecting bicuculline evoked positive chronotropy and
inotropy; iii) Alfa adrenergic receptors control cardiac function; iv) Beta adrenergic
receptors of PVH do not influence cardiac function; v) afterload seems to poorly contribute
to the PVH-evoked inotropy. Jointly, our results suggest that PVH provides substantial
contribution to the tonic control of cardiac function. We conclude that the PVH participates
in the control of cardiac function. Changes in the activity of these neurons by gabaergic
and adrenergic influences may set autonomic control of cardiac function, thus resulting in
contractile and heartbeat responses. Deepen the knowledge on the mechanisms
underlying the control of central areas and its influence on the cardiovascular system may
feed the understanding of cardiovascular pathophysiology.
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MENDONÇA, Michelle Mendanha. Contribuição de diferentes sinapses do hipotálamo paraventricular para o controle da função cardíaca. 2017. 87 f. Dissertação (Mestrado em Biologia) - Universidade Federal de Goiás, Goiânia, 2017.