Melatonin modulates baroreflex control via area postrema

Authors

  • Luciana A. Campos,

    Corresponding author
    1. Department of Physiology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
    • São José dos Campos Technology Park, University Camilo Castelo Branco (UNICASTELO), São Paulo, Brazil
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  • Jose Cipolla-Neto,

    1. Department of Physiology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
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  • Lisete C. Michelini

    1. Department of Physiology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
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Correspondence

Luciana A. Campos, University Camilo Castelo Branco (UNICASTELO), São José dos Campos Technology Park, Rod. Presidente Dutra Km 138, São José dos Campos, Sao Paulo 12247-004, Brazil. Tel/Fax: + 55 12 3905 4401; E-mail: camposbaltatu@yahoo.com

Abstract

Pineal gland and its hormone melatonin have been implicated in modulation of cardiovascular system. We aimed at studying the effects of melatonin on baroreflex sensitivity and the role of area postrema, as a component modulator of baroreflex arch. Mean arterial pressure (MAP) and heart rate (HR) were recorded in conscious freely moving rats. Baroreceptor reflex sensitivity was assessed by determining the HR responses to ramped infusions of phenylephrine (PE) and sodium nitroprusside (SNP)-induced MAP changes. Melatonin bolus (0.11 mg/kg) immediately followed by its continuous infusion (0.43 × 10−9 mol/L at a rate of 0.65 mL/h for 30 min) in healthy normotensive rats produced a downward shift of baroreceptor reflex control with a substantial inhibition of reflex tachycardia (−32%) and potentiation of reflex bradycardia (+20%). Ablation of area postrema (APX group) induced a sustained decrease of MAP (101 ± 3 vs. 116 ± 3 mmHg, P < 0.05 in comparison with sham rats, respectively). The melatonin-induced alterations of baroreflex function observed in the sham group were abolished in the APX group. We conclude that circulating melatonin can modulate baroreceptor reflex control of HR, thus resetting it toward lower HR values. The modulatory effects of melatonin may be mediated via melatonin receptors in the area postrema, located outside the blood–brain barrier.

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