Optogenetic Study of Anterior BNST and Basomedial Amygdala Projections to the Ventromedial Hypothalamus

Abstract

The basomedial amygdala (BM) influences the ventromedial nucleus of the hypothalamus (VMH) through direct glutamatergic projections as well as indirectly, through the anterior part of the bed nucleus of the stria terminalis (BNSTa). However, BM and BNSTa axons end in a segregated fashion in VMH. BM projects to the core of VMH, where VMH’s projection cells are located, whereas BNSTa projects to the shell of VMH, where GABAergic cells that inhibit core neurons are concentrated. However, the consequences of this dual regulation of VMH by BM and BNSTa are unknown. To study this question, we recorded the responses of VMH’s shell and core neurons to the optogenetic activation of BM or BNSTa inputs in transgenic mice that selectively express Cre-recombinase in glutamatergic or GABAergic neurons. Glutamatergic BM inputs fired most core neurons but elicited no response in GABAergic shell neurons. Following BM infusions of AAV-EF1α-DIO-hChR2-mCherry in Vgat-ires-Cre-Ai6 mice, no anterograde labeling was observed in the VMH, suggesting that GABAergic BM neurons do not project to the VMH. In contrast, BNSTa sent mostly GABAergic projections that inhibited both shell and core neurons. However, BNSTa-evoked IPSPs had a higher amplitude in shell neurons. Since we also found that activation of GABAergic shell neurons causes an inhibition of core neurons, these results suggest that depending on the firing rate of shell neurons, BNSTa inputs could elicit a net inhibition or disinhibition of core neurons. Thus, the dual regulation of VMH by BM and BNSTa imparts flexibility to this regulator of defensive and social behaviors.

Direct Medial Entorhinal Cortex Input to Hippocampal CA3 Is Crucial for eEF2K Inhibitor-Induced Neuronal Oscillations in the Mouse Hippocampus

“…In this way, afferents from the entorhinal cortex to the CA3 neurons (Neves et al, 2008) remained functional in acute slices. We also confirmed the presence of entorhinal cortex-hippocampal afferents in acute slices utilizing tracing experiments (Tervo et al, 2016;Yamamoto et al, 2018) and dual recordings from entorhinal cortex and CA3 area. These data are in line with another publication demonstrating the presence of intact entorhinal cortex to hippocampus afferents in the str.…”

Novel objects elicit greater activation in the basolateral complex of the amygdala of wild rats compared with laboratory rats

“…As a result, the HPA axis response is elicited. The BLA activation is simultaneously transmitted to the basomedial nucleus of the amygdala [26] and then to the VMH [48]. The VMH activation is further transmitted to the anterior hypothalamus [46] and induces avoidance behavior.…”

Sexual dimorphism, estrous cycle and laterality determine the intrinsic and synaptic properties of medial amygdala neurons in rat

“…Here, we demonstrated that the two classes of MePD inhibitory neurons in males received predominant excitatory inputs. Previous studies have shown that MePD neurons project to the BNST, the main efferent pathway in males (de Olmos et al, 2004;Pardo-Bellver et al, 2012), containing mostly GABAergic cells (Poulin et al, 2009;Yamamoto et al, 2018) and projecting to the hypothalamus (Dong et al, 2001). Therefore, the MePD neurons could disinhibit the hypothalamic cells via an indirect pathway, by inhibiting BNST GABAergic cells.…”