Local Metabolism of Ethanol to Acetic Acid/Acetate in the Central Nucleus of Amygdala Elicits Sympathoexcitatory Responses through Activation of NMDAR in Sprague Dawley Rats

Abstract

ABSTRACTAimBinge alcohol consumption elicits robust sympathoexcitation and excitatory neuronal output. However, the central mechanism that mediates these effects remains elusive. We investigated the effects of ethanol metabolism within the central nucleus of the amygdala (CeA) on sympathoexcitation, and elucidated the role of acetate in these excitatory responses.MethodsIn vivo arterial blood pressure, heart rate and sympathetic nerve activity responses to CeA microinjected ethanol or acetate with appropriate inhibitors/antagonists were tracked. In vitro whole-cell electrophysiology recording responses to acetate in CeA neurons with axon projecting to the rostral ventrolateral medulla (CeA-RVLM) were investigated, and cytosolic calcium responses in primary neuronal cultures were quantified.ResultsWe demonstrate that in Sprague Dawley rats, local brain metabolism of ethanol in the CeA to acetic acid/acetate elicits sympathoexcitatory responses in vivo through activation of NMDAR. Aldehyde dehydrogenase inhibition using cyanamide and NMDAR antagonism using AP5 or memantine blunted these effects. Whole-cell patch-clamp recordings in brain slices containing autonomic CeA-RVLM neurons revealed a dose-dependent increase in neuronal excitability in response to acetate. The NMDAR antagonists AP5 and memantine suppressed the acetate-induced increase in CeA-RVLM neuronal excitability, as well as the direct activation of NMDAR-mediated inward currents by acetate in brain slices. We observed that acetate increased cytosolic Ca2+ in a time-dependent manner in primary neuronal cell cultures. The acetate enhancement of calcium signaling was abolished by memantine.ConclusionThese findings suggest that within the CeA, ethanol is sympathoexcitatory through local brain metabolism, which generates acetic acid/acetate leading to activation of NMDAR.