Fig. 7: Connections of BLAp, BMAp, and BLAv.
From: Connectivity characterization of the mouse basolateral amygdalar complex
a Anterograde maps showing BLAp and BMAp neuron projections to BST. BLAp neurons target lateral parts of BST, while those in BMAp target medial BST. b–c Validation of BLAp projections to BST. Retrograde tracers in BSTov/ju/rh (b) and BSTal (c) back-label BLAp neurons validating the BLAp→BSTal/ov/ju/rh projections. Note the absence of labels in BMAp. Insets are magnification of injection site regions. d Validation of BMAp→BSTam/pr projection. Retrograde tracer injection placed more medially than those in (b) and (c) (BSTam included) now labels BMAp neurons and some neurons in BLA.ac and LA. Inset shows magnification of injection site region. BST bed nucleus of stria terminalis, BSTov BST oval nucleus, BSTju BST juxstacapsular nucleus, BSTrh BST rhomboid nucleus, BSTal BST anterolateral nucleus, BSTam BST anteromedial nucleus, BSTpr principal nucleus. e Top panels: BLAp neurons project to rostral (LSr) and caudal (LSc) lateral septal nuclei and BMAp projects to LSr. Bottom panels validate these connections (BLAp→LSr/c and BMAp→LSr). Retrograde injection in dorsomedial hypothalamic nucleus (DMH: f) and anterior hypothalamic nucleus (AHN: g) validates BMAp neuron projections to the hypothalamic regions (BMAp→DMH/AHN). h Validation of BMAp/BLAp to lateral hypothalamic area (LHA) via LHA retrograde injection. Ellipses on anterograde maps denote location of retrograde injection for validation. i Summarized brain-wide connections of BLAp neurons. j Summarized brain-wide connections of BMAp neurons. For full list of abbreviations see Table 1. k FG injection in medial preoptic nucleus (MPN)/medial preoptic area (MPO) validates BMAp neuron projections to those hypothalamic nuclei (BMAp→MPN/MPO). l CTb injection in lateral preoptic area (LPO) validates BLAp neuron projections to the hypothalamic nucleus (BLAp→LPO). Ellipses on anterograde maps to the left denote location of retrograde tracer injections. m Top panels: projections from BLA.am, BLA.al, BLA.ac, BLAp, BMAp, BLAv, and LA to the tuberal region of LHA and to ventromedial hypothalamic area (VMH). Strongest projections to VMH are from BMAp neurons, and strongest input to LHA are from BLAp and BMAp neurons. Bottom panels validate these connections. Retrograde tracer injections 1 (CTb) and 2 (FG) in LHA back-label both BLAp and BMAp projection neurons (BMAp/BLA→LHA), while FG injection 3 in VMH back-labels selectively BMAp projection neurons (BMAp→VMH). Insets show magnification of injection site regions. n Top panels: retrograde maps showing SUBv back-labeled cells from retrograde tracer injections in BLAp and BMAp (left) and CA1v labeled cells from BMAp retrograde tracer injection (right). Ellipses denote locations of PHAL injections in bottom panels. Bottom panels: PHAL injection in SUBv labels BLA.ac, BLAp, and BMAp validating SUBv→BLA.ac/BLAp/BMAp connections. PHAL injection in CA1v labels fibers in BLA.ac and BMAp, but not BLAp validating the CA1v→BLA.ac/BMAp connections. o Summarized brain-wide connections of BLAv neurons. For full list of abbreviations see Table 1. p Shows location of BLAv. q Top panels show anterograde projections from BLAv, while bottom ones show projections from intermediodorsal thalamic nucleus (IMD). Note the similarity in labeling from the two injection cases in GU (gustatory cortical area), AId (agranular insular area, dorsal part), CPi.vm (CP intermediate, ventromedial), CPc.v (CP caudal, ventral), and ENTl (entorhinal cortical area, lateral part) particularly layer V. r FG injection in CPi.vm/vl back-labels BLA.al and BLAv projection neurons (BLA.al/BLAv→CPi.vm/vl), but also neurons in thalamic nuclei CM (central medial) and IMD. s–t FG injection in CP caudal ventromedial, where BLAv and IMD project, back-labels neurons in regions proposed to be involved in gustatory/visceral processing like IMD, CM, VISC (visceral cortical area), MOp mouth regions, GU (gustatory cortical area), and AI (agranular insular cortical area). u Like the BLAv and IMD, the AI also projects to ENTl(V). v A PHAL injection in ENTl(V) shows that it projects back to BLAv, but also to BLA.al [ENTl(V)→BLAv/BLA.al].
