Abstract
The amygdala, which is involved in various behaviors and emotions, is reported to connect with the whole brain. However, the long-range inputs of distinct cell types have not yet been defined. Here, we used a retrograde trans-synaptic rabies virus to generate a whole-brain map of inputs to the main cell types in the mouse amygdala. We identified 37 individual regions that projected to neurons expressing vesicular glutamate transporter 2, 78 regions to parvalbumin-expressing neurons, 104 regions to neurons expressing protein kinase C-δ, and 89 regions to somatostatin-expressing neurons. The amygdala received massive projections from the isocortex and striatum. Several nuclei, such as the caudate-putamen and the CA1 field of the hippocampus, exhibited input preferences to different cell types in the amygdala. Notably, we identified several novel input areas, including the substantia innominata and zona incerta. These findings provide anatomical evidence to help understand the precise connections and diverse functions of the amygdala.
Highlights
As a hub responsible for the control of diverse behaviors and the modulation of different emotions such as fear, anxiety, and reward, the amygdala is reported to connect to a large number of brain regions [1,2,3,4,5,6,7]
To provide anatomical evidence to help understand the precise connections and diverse functions of the amygdala, we developed a detailed map of the whole-brain long-range inputs to the amygdala and analyzed the distributions of inputs to the four main cell types in the amygdala
The results showed that different cell subtypes in the basolateral amygdala (BLA) and central nucleus of the amygdala (CeA) received a comparable number of input cells per starter cell (Fig. 1B–E)
Summary
As a hub responsible for the control of diverse behaviors and the modulation of different emotions such as fear, anxiety, and reward, the amygdala is reported to connect to a large number of brain regions [1,2,3,4,5,6,7]. Previous studies have reported the long-range connectivity of the CeA, including inputs from the BLA, paraventricular thalamic nucleus (PVT), mPFC, bed nucleus of the stria terminalis (BST), and raphe nucleus, and output projections to the periaqueductal grey, nucleus tractus solitarius, locus coeruleus, and hypothalamus [14,15,16]. Various studies have explored the innervation of the amygdala and its outputs, research on whole-brain inputs to specific cell types in the BLA and CeA is lacking. The BLA is composed of a majority (80%–85%) of spiny glutamatergic neurons and a minority (20%) of GABAergic neurons, including parvalbumin-expressing (PV?) interneurons [17,18,19,20,21]
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