A bed nucleus of stria terminalis neuronal ensemble mediates inflammation-induced sleep alterations in male mice.

Systemic inflammation disrupts sleep-wake homeostasis, leading to excessive sleep and fragmented sleep architecture. The neural substrates that mediate these inflammation-induced sleep alterations remain poorly defined. The bed nucleus of the stria terminalis (BNST), a forebrain region integrating limbic signals, represents a candidate neural substrate linking peripheral inflammation to sleep alterations. We hypothesized that inflammatory signals activate specific BNST neuronal ensembles that mediate inflammation-induced sleep alterations. To test this hypothesis, we examined sleep-wake patterns and brain-wide c-Fos expression in mice following lipopolysaccharide (LPS) administration. LPS treatment significantly reduced wake time, increased non-rapid eye movement (NREM) sleep duration, and enhanced sleep fragmentation. c-Fos mapping revealed robust activation of BNST neurons after LPS challenge. Using targeted recombination in active populations (TRAP2) strategy to label LPS-activated BNST ensembles (BNSTLPS), fiber photometry recordings confirmed that these tagged neurons exhibited increased calcium responses to subsequent LPS exposure. Chemogenetic inhibition or lesioning of BNSTLPS neurons attenuated LPS-induced increase in NREM sleep duration and reduction in wakefulness, and reduced peripheral pro-inflammatory cytokine levels, whereas chemogenetic activation of BNSTLPS neurons under baseline conditions recapitulated these sleep changes without elevating cytokine levels. Methylprednisolone administration suppressed BNST activation and reversed LPS-induced sleep alterations. These findings demonstrate that BNSTLPS neurons not only regulate inflammation-induced NREM sleep increase but also partially modulate peripheral cytokine levels, suggesting BNSTLPS activity as a potential therapeutic target for inflammation-related sleep disorders.