Neonatal stress is associated with region‐specific changes in mitochondrial respiration and sex‐dependent respiratory instability in adulthood

Early-life stress is increasingly recognized as a critical determinant of brain development, yet its long-term impact on the neural control of breathing remains poorly defined. Here we show that neonatal maternal separation (NMS, P3-P12) induces long-term alterations in respiratory stability and mitochondrial function within respiratory circuits. In adulthood, NMS altered respiratory stability, with significant treatment × sex interactions for total and postsigh apnoeas; post hoc comparisons showed increased frequencies of these apnoeic events in males. Sigh frequency also showed a significant main effect of treatment. Region-specific high-resolution respirometry showed that NMS was associated with reduced mitochondrial respiration in the paraventricular hypothalamus (PVH) and increased mitochondrial respiration in the nucleus tractus solitarius (NTS) and ventral respiratory column (VRC), without significant treatment × sex interactions. Normalization to cytochrome c oxidase (COX) activity largely eliminated these differences, suggesting that changes in absolute respiration are consistent with a contribution of differences in mitochondrial content rather than major alterations in respiratory capacity relative to mitochondrial abundance. In the pre-Bötzinger complex, absolute mitochondrial respiration was preserved, whereas oxygen consumption rate (OCR)/COX ratios revealed treatment-dependent alterations in mitochondrial respiratory flux relative to mitochondrial content. NMS also altered the expression of selected genes involved in mitochondrial biogenesis, mitophagy, fusion and fission in the NTS and VRC, with significant main effects of treatment and sex but no treatment × sex interactions. Oxidative and inflammatory markers were largely preserved, although selective effects of sex and treatment were detected. Together, these findings demonstrate that neonatal stress produces persistent, region-specific remodelling of mitochondrial and molecular pathways within respiratory circuits, accompanied by sex-dependent vulnerability to respiratory instability. KEY POINTS: Early-life stress induces a persistent, sex-dependent disruption of respiratory control, increasing apnoeas in adult males, whereas females remain comparatively resistant. This phenotype is associated with region-specific remodelling of mitochondrial function along the paraventricular hypothalamus (PVH)-brainstem axis, characterized by reduced hypothalamic respiration and increased brainstem mitochondrial respiration after neonatal stress. Neonatal stress alters transcriptional pathways involved in mitochondrial biogenesis, mitophagy and dynamics within respiratory brainstem regions, revealing persistent molecular remodelling associated with early-life adversity.