Angiotensin II facilitates GABAergic neurotransmission at postsynaptic sites in rat amygdala neurons

The central nucleus of the amygdala (CeA) is critical in the regulation of sodium appetite. Angiotensin II (Ang II) is important in the generation of sodium appetite and may function as a neurotransmitter or modulator to affect the synaptic transmission and the excitability of neurons. However, the role of Ang II in the CeA remains unclear. In this study, we determined the effects of Ang II on the excitatory and inhibitory synaptic inputs to the CeA neurons in brain slices with whole-cell patch-clamp recordings. Ang II (0.5-5 μM) significantly potentiated the amplitude of spontaneous GABAergic inhibitory postsynaptic currents (IPSCs) in a concentration-dependent manner. Ang II (2 μM) significantly increased the amplitude of miniature GABAergic inhibitory postsynaptic currents (mIPSCs) without affecting the frequency. This effect was blocked by Ang II type 1 (AT₁) receptor antagonist, losartan. One mM guanosine 5'-O-(-2-thiodiphosphate) (GDP-β-s) in the pipette internal solution eliminated the facilitatory effect of Ang II on GABAergic synaptic transmission. In contrast, Ang II had no effect on the spontaneous glutamatergic excitatory postsynaptic currents (EPSCs) and did not alter the frequency and amplitude of miniature EPSCs at concentrations that facilitated IPSCs. Furthermore, Ang II decreased the firing activity of CeA neurons, and this effect was abolished by losartan and GDP-β-s. In addition, Ang II failed to inhibit CeA neurons in the presence of bicuculline. These data provide substantial new evidence that Ang II inhibits the CeA neurons by facilitation of GABAergic synaptic input efficacy through activation of postsynaptic AT₁ receptors.