The central amygdala (CeA) and BNST are also key components of the extended amygdala circuitry that are affected by ethanol exposure and influence drinking, withdrawal and relapse. These forebrain regions can influence the function of the three C-BG-C circuits through projections to the midbrain. The BNST and CeA project to both the VTA and SNc, providing GABAergic and glutamatergic inputs that can directly or indirectly influence the dopaminergic connections with key roles in reward- and reinforcement-based learning (Watabe-Uchida, Zhu et al. 2012, Jennings, Sparta et al. 2013). Newly-discovered monosynaptic GABAergic projections from the BNST to the DS (Smith et al., 2016) may also provide another source of integration between the extended amygdala and associative basal ganglia that could mediate stress effects on operant and ethanol-related behaviors. As yet, there is little evidence as to whether and how these projections influence the functions of the C-BG-C circuits, let alone how ethanol alters these influences, and this is a research area that is primed for exploration.
