GABA in the central amygdaloid nucleus modulates the electrolyte excretion and hormonal responses to blood volume expansion in rats

• Published in: Brazilian journal of medical and biological research Vol. 42; no. 1; pp. 114 - 121
• Main Authors: Margatho, L O, Elias, L L K, Antunes-Rodrigues, J
• Format: Journal Article
• Language: English; Portuguese
• Published: Brazil Associação Brasileira de Divulgação Científica 01.01.2009
• Subjects: Amygdala - drug effects; Amygdala - physiology; Animals; Atrial Natriuretic Factor - blood; Atrial natriuretic peptide; Bicuculline - administration & dosage; Bicuculline - pharmacology; BIOLOGY; Blood Volume - drug effects; Blood Volume - physiology; Central amygdaloid nucleus; Diuresis - drug effects; Diuresis - physiology; GABA Agonists - administration & dosage; GABA Agonists - pharmacology; GABA Antagonists - administration & dosage; GABA Antagonists - pharmacology; Male; MEDICINE, RESEARCH & EXPERIMENTAL; Muscimol - administration & dosage; Muscimol - pharmacology; Natriuresis; Oxytocin; Oxytocin - blood; Rats; Rats, Wistar; Sodium - urine; Urine output; Central amygdaloid nucleus; Atrial natriuretic peptide; Natriuresis; Oxytocin; Urine output
• ISSN: 0100-879X; 1414-431X; 1414-431X; 0100-879X
• DOI: 10.1590/S0100-879X2009000100016

We investigated the involvement of GABAergic mechanisms of the central amygdaloid nucleus (CeA) in unanesthetized rats subjected to acute isotonic or hypertonic blood volume expansion (BVE). Male Wistar rats bearing cannulas unilaterally implanted in the CeA were treated with vehicle, muscimol (0.2 nmol/0.2 microL) or bicuculline (1.6 nmol/0.2 microL) in the CeA, followed by isotonic or hypertonic BVE (0.15 or 0.3 M NaCl, 2 mL/100 g body weight over 1 min). The vehicle-treated group showed an increase in sodium excretion, urinary volume, plasma oxytocin (OT), and atrial natriuretic peptide (ANP) levels compared to control rats. Muscimol reduced the effects of BVE on sodium excretion (isotonic: 2.4 +/- 0.3 vs vehicle: 4.8 +/- 0.2 and hypertonic: 4.0 +/- 0.7 vs vehicle: 8.7 +/- 0.6 microEq.100 g-1.40 min-1); urinary volume after hypertonic BVE (83.8 +/- 10 vs vehicle: 255.6 +/- 16.5 microL.100 g-1.40 min-1); plasma OT levels (isotonic: 15.3 +/- 0.6 vs vehicle: 19.3 +/- 1 and hypertonic: 26.5 +/- 2.6 vs vehicle: 48 +/- 3 pg/mL), and ANP levels (isotonic: 97 +/- 12.8 vs vehicle: 258.3 +/- 28.1 and hypertonic: 160 +/- 14.6 vs vehicle: 318 +/- 16.3 pg/mL). Bicuculline reduced the effects of isotonic or hypertonic BVE on urinary volume and ANP levels compared to vehicle-treated rats. However, bicuculline enhanced the effects of hypertonic BVE on plasma OT levels. These data suggest that CeA GABAergic mechanisms are involved in the control of ANP and OT secretion, as well as in sodium and water excretion in response to isotonic or hypertonic blood volume expansion.