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

Author(s)

L.O. Margatho ^[1] ; L.L.K. Elias ^[2] ; J. Antunes-Rodrigues ^[3]

Affiliation

^[1] Universidade de São Paulo. Faculdade de Medicina de Ribeirão Preto. Departamento de Fisiologia - Brasil

^[2] Universidade de São Paulo. Faculdade de Medicina de Ribeirão Preto. Departamento de Fisiologia - Brasil

^[3] Universidade de São Paulo. Faculdade de Medicina de Ribeirão Preto. Departamento de Fisiologia - Brasil

• Document type: Journal article
• Source: Brazilian Journal of Medical and Biological Research; v. 42, n. 1, p. 114-121, 2009-01-00.

Abstract

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 µL) or bicuculline (1.6 nmol/0.2 µL) 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 µEq·100 g-1·40 min-1); urinary volume after hypertonic BVE (83.8 ± 10 vs vehicle: 255.6 ± 16.5 µL·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. (AU)

• FAPESP's process: 03/00327-8 - Integrative studies of the body fluid homeostasis: physiological and molecular aspects of the neuroendocrine control and clinical and experimental evaluation
• Grantee: José Antunes Rodrigues
• Support Opportunities: Research Projects - Thematic Grants