Fig. 1: Comparison of the hyperventilatory response to CO₂ inhalation (5% CO₂; 10 min) between adult females raised under standard conditions or subjected to neonatal maternal separation (NMS) across the different phase of the estrus cycle.

A Original plethysmographic recording comparing ventilatory activity at rest and at the onset of CO₂ inhalation (blue arrow) in a female raised under control conditions (top trace) versus a female subjected to neonatal maternal separation (bottom trace; NMS: 3 h/day; postnatal days 3–12). B The breathing frequency response expressed as a percentage change from baseline (room air). 17β-estradiol (E₂) levels across the estrus cycles measured C while breathing room air (baseline) and D 30 min following CO₂ inhalation test (5% CO₂; 10 min). E Regression analysis comparing the relationship between E₂ levels during proestrus (post-CO₂; blue box) and the intensity of the breathing frequency response to CO₂ between NMS (red circles) and control females (white circles). Box plots: the top and bottom boundaries of the box indicate the 25^th and 75^th percentile, respectively. Within the box, the black bar indicates the median; the other bar (red or white) indicate the mean. The error bars indicate the 10^th and 90^th percentiles. The numbers in brackets below the boxes indicate the number of replicates in each group. Post hoc pairwise comparisons were performed only when warranted by ANOVA. *Indicates a value different from corresponding proestrus value at P < 0.05. ^†Indicates a value different from corresponding control value at P < 0.05.