A network of basolateral amygdala projection neurons contributes to stress-induced activation of the hypothalamic-pituitary-adrenal axis.

The basolateral amygdala (BLA) is reliably activated by psychological stress in both humans and rodents and influences diverse behavioral and physiological processes involved in stress adaptation. However, functional organization of distinct BLA circuits and their contribution to stress-induced activation of the neuroendocrine response is unclear. We establish four major findings in adult male rats: (i) BLA projection neurons are necessary and sufficient for stress-induced neuroendocrine activation; (ii) projection populations have a heterogeneous spatial distribution across the BLA; (iii) diverse BLA populations targeting the prelimbic cortex, nucleus accumbens, bed nucleus of stria terminalis, central amygdala, lateral hypothalamus, and ventral hippocampus are activated by acute stress, with the location of activated populations biased toward the medial basal amygdala; and (iv) inhibition of singular projections does not recapitulate global inhibition of BLA projection neurons. Together, this suggests that a network of BLA projection populations is broadly activated by acute stress and collectively contribute to neuroendocrine regulation.