Locus coeruleus to basolateral amygdala noradrenergic projections promote anxiety-like behavior

PB (Parabrachial nucleus) MBA:867 projects to BLA (Basolateral amygdalar nucleus) MBA:295 · Mouse

Besides TH-positive LC cells, Fluorogold injected in the BLA also back-labelled TH-negative neurons dorsal and ventral to the LC; the authors suggest these probably belong to the medial parabrachial nucleus, but their identity was not confirmed.

Fig. 1B and legend

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LC (Locus ceruleus) MBA:147 projects to BLA (Basolateral amygdalar nucleus) MBA:295 · Mouse

A Cre-dependent eYFP reporter virus injected into the LC of Th-Cre mice filled LC somata and revealed labelled axonal fibres terminating within the BLA of the same animals.

Fig. 1E–H

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BLA (Basolateral amygdalar nucleus) MBA:295 projects to ACB (Nucleus accumbens) MBA:56 · Mouse

Cholera toxin subunit B deposited in the nucleus accumbens retrogradely labelled BLA neurons; these accumbens-projecting cells showed less cFos after LC terminal stimulation than the hippocampus- or central amygdala-projecting cells.

Fig. 4C–G; Fig. 4—figure supplement 1F

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BLA (Basolateral amygdalar nucleus) MBA:295 projects to CEA (Central amygdalar nucleus) MBA:536 · Mouse

Cholera toxin subunit B injected into the central amygdala back-labelled BLA neurons, a population that showed substantial cFos expression after photostimulation of LC terminals in the BLA.

Fig. 4C–G; Fig. 4—figure supplement 1H

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LC (Locus ceruleus) MBA:147 functionally connects to BLA (Basolateral amygdalar nucleus) MBA:295 · Mouse

Light activation of ChR2-expressing LC terminals in BLA slices evoked catecholamine transients with voltammetric signatures of norepinephrine (clearance t1/2 about 2 s) that fell to roughly a third of baseline after reserpine. In vivo, the same terminal stimulation raised firing in a fifth of recorded BLA units and suppressed firing in a smaller fraction, with long response latencies indicating a neuromodulatory rather than fast monosynaptic action, and increased BLA cFos relative to opsin-negative and contralateral controls; intra-BLA beta-adrenergic blockade abolished the behavioural consequence.

Fig. 2C–F; Fig. 3C–K; Fig. 4B

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BLA (Basolateral amygdalar nucleus) MBA:295 projects to HIP (Hippocampal region) MBA:1080 · Mouse

Cholera toxin subunit B placed in the ventral hippocampus retrogradely labelled a population of BLA neurons, which overlapped strongly with cFos induced by LC terminal photostimulation.

Fig. 4C–G; Fig. 4—figure supplement 1G

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LC (Locus ceruleus) MBA:147 projects to BLA (Basolateral amygdalar nucleus) MBA:295 · Mouse

Fluorogold deposited in the BLA of wild-type mice retrogradely labelled tyrosine hydroxylase-positive cells in the locus coeruleus. In a second approach, red retrobeads placed in the BLA of Th-Cre mice that had received a Cre-dependent ChR2-eYFP virus in the LC produced cells containing both markers, identifying BLA-projecting catecholaminergic LC neurons.

Fig. 1A–D

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