title: Functional evidence of paraventricular nucleus involvement in cardiovascular and autonomic modulation in response to acute microgravity (head-down tilt) in unanesthetized rats.
abstract: Exposure to microgravity induces autonomic and vestibular disorders such as alterations in cardiovascular function. The paraventricular nucleus of the hypothalamus (PVN) is known to be an important center for integrating autonomic and cardiovascular responses as blood volume reflexes. The acute effects promoted by microgravity and PVN involvement in cardiovascular and autonomic parameters have not yet been evaluated. Male Wistar rats were anesthetized to facilitate cannulae implantation in the PVN. After 3 days of surgical recovery, femoral artery and vein catheters were implanted for direct recording of blood pressure and heart rate (HR) in conscious animals to evaluate cardiovascular and autonomic changes in an acute protocol of head-down tilt (HDT) in nonanesthetized rats. During HDT, there was an increase in mean arterial pressure (11 ± 1 mmHg, P < 0.05) and a decrease in HR (-28 ± 5 bpm, P < 0.05). Spectral analysis of systolic arterial pressure showed an increase in the low-frequency (LF) component. In addition, HDT induced a reduction in the LF component and an increase in the high-frequency (HF) component of the pulse interval (PI). PVN inhibition with muscimol reversed bradycardia and blocked the reduction of the LF and HF increases in PI during HDT. These results suggest that the PVN participates in the cardiovascular compensation during HDT, especially modulating cardiac responses.
authors.affiliation: Department of Physiological Sciences, State University of Londrina, Londrina, Paraná Region, Brazil.
authors.forename: Eric Diego Turossi
authors.initials: ED
authors.lastname: Amorim
authors.affiliation: Department of Physiological Sciences, State University of Londrina, Londrina, Paraná Region, Brazil.
authors.forename: Vivian Rossi
authors.initials: VR
authors.lastname: Peras
authors.affiliation: Department of Physiological Sciences, State University of Londrina, Londrina, Paraná Region, Brazil.
authors.forename: Ozahyr
authors.initials: O
authors.lastname: de Andrade
authors.affiliation: Department of Physiological Sciences, State University of Londrina, Londrina, Paraná Region, Brazil.
authors.forename: Marli Cardoso
authors.initials: MC
authors.lastname: Martins-Pinge
mesh_terms: D000818:Animals; D017704:Baroreflex / Q000187:drug effects / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D018475:Head-Down Tilt / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008845:Microinjections / Q000379:methods; D009118:Muscimol / Q000008:administration & dosage; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D014893:Weightlessness
chemical_list: D009118:Muscimol
keywords: arterial pressure; cobalt chloride; heart rate; muscimol; parasympathetic; sympathetic