BACKGROUND: Orexins are hypothalamic neuropeptides recently involved in the regulation of emotional memory. The basolateral amygdala, an area orchestrating fear memory processes, appears to be modulated by orexin transmission during fear extinction. However, the neuronal types within the basolateral amygdala involved in this modulation remain to be elucidated. METHODS: We used retrograde tracing combined with immunofluorescence techniques in mice to identify basolateral amygdala projection neurons and cell subpopulations in this brain region influenced by orexin transmission during contextual fear extinction consolidation. RESULTS: Treatment with the orexin-1 receptor antagonist SB334867 increased the activity of basolateral amygdala neurons projecting to infralimbic medial prefrontal cortex during fear extinction. GABAergic interneurons expressing calbindin, but not parvalbumin, were also activated by orexin-1 receptor antagonism in the basolateral amygdala. CONCLUSIONS: These data identify neuronal circuits and cell populations of the amygdala associated with the facilitation of fear extinction consolidation induced by the orexin-1 receptor antagonist SB334867.

This work was supported by “Plan Nacional sobre Drogas” (no. 2014I019 to F.B.), the “Ministerio de Economía y Competitividad-MINECO” (no. SAF2014-59648-P to R.M.), the “Instituto de Salud Carlos III” (no. PI13/00042 to F.B. and RETICS-RTA, no. RD12/0028/0023 to R.M.), the “Generalitat de Catalunya-AGAUR” (no. 2014-SGR-1547 and ICREA-Acadèmia (2015) to R.M.). AF was recipient of an EMBO Short-Term Fellowship (281-2015).