Neuropeptides in the posterodorsal medial amygdala modulate central cardiovascular reflex responses in awake male rats

• Published in: Brazilian journal of medical and biological research 2015-02, Vol.48 (2), p.128-139
• Main Authors: Quagliotto, E, Casali, K R, Dal Lago, P, Rasia-Filho, A A
• Format: Article
• Language: English
• Subjects: Amygdala (Brain); Analysis; Analysis of Variance; Angiotensin II; Angiotensin II - administration & dosage; Animals; Arterial Pressure - drug effects; Baroreceptor and chemoreceptor reflexes; Baroreflex - drug effects; BIOLOGY; Biomedical Sciences; Brain - anatomy & histology; Cardiovascular System - innervation; Chemoreceptors; Corticomedial Nuclear Complex - drug effects; Corticomedial Nuclear Complex - metabolism; Health aspects; Heart Rate - drug effects; Hemodynamics - drug effects; Male; MEDICINE, RESEARCH & EXPERIMENTAL; Microinjections; Neuropeptides; Neuropeptides - administration & dosage; Neuropeptides - pharmacology; Oxytocin; Oxytocin - administration & dosage; Parasympathetic Nervous System - drug effects; Power spectral analysis; Rats, Wistar; Somatostatin; Somatostatin - administration & dosage; Statistics, Nonparametric; Symbolic analysis; Sympathetic Nervous System - drug effects; Vascular Access Devices; Wakefulness
• ISSN: 0100-879X; 1414-431X; 1414-431X
• DOI: 10.1590/1414-431X20144095

The rat posterodorsal medial amygdala (MePD) links emotionally charged sensory stimuli to social behavior, and is part of the supramedullary control of the cardiovascular system. We studied the effects of microinjections of neuroactive peptides markedly found in the MePD, namely oxytocin (OT, 10 ng and 25 pg; n=6/group), somatostatin (SST, 1 and 0.05 μM; n=8 and 5, respectively), and angiotensin II (Ang II, 50 pmol and 50 fmol; n=7/group), on basal cardiovascular activity and on baroreflex- and chemoreflex-mediated responses in awake adult male rats. Power spectral and symbolic analyses were applied to pulse interval and systolic arterial pressure series to identify centrally mediated sympathetic/parasympathetic components in the heart rate variability (HRV) and arterial pressure variability (APV). No microinjected substance affected basal parameters. On the other hand, compared with the control data (saline, 0.3 µL; n=7), OT (10 ng) decreased mean AP (MAP50) after baroreflex stimulation and increased both the mean AP response after chemoreflex activation and the high-frequency component of the HRV. OT (25 pg) increased overall HRV but did not affect any parameter of the symbolic analysis. SST (1 μM) decreased MAP50, and SST (0.05 μM) enhanced the sympathovagal cardiac index. Both doses of SST increased HRV and its low-frequency component. Ang II (50 pmol) increased HRV and reduced the two unlike variations pattern of the symbolic analysis (P