Effect of noradrenergic inputs on the cardiovascular depressor responses to stimulation of central nucleus of the amygdala

Experiments were done in chloralose anesthetized, paralyzed and artificiall y ventilated male Wistar rats to investigate the effects of microinjections of either norepinephrine (NE) or tyramine into the central nucleus of the amygdala (ACe) on the arterial pressure (AP) and heart rate (HR) responses elicited by glutamate (Glu) stimulation of the ACe. Microinjections of Glu into the ACe elicited decreases in mean AP (- 23 +/- 3 mmHg) and HR (- 11 /- 3 bpm). Microinjections of NE or tyramine into these sites did not elici t cardiovascular responses. However, Glu into the ACe in the presence of NE or tyramine elicited depressor or bradycardic response that were significa ntly smaller (70-100%) in magnitude than to Glu alone. These data suggest t hat noradrenergic mechanisms in the ACe alter the excitability of ACe neuro ns involved in mediating changes in systemic AP and HR. (C) 1999 Elsevier S cience B.V. All rights reserved.