We hypothesized that administration of estradiol benzoate to males and testosterone propionate to female neonatal rat pups alters sex-specific ventilatory responses to aspartic acid with correspondent changes in N-methyl-D-aspartate receptor subunit 1 (NR1) expression determined by Western blot in specific brain regions. One-day-old rat pups received estradiol benzoate, testosterone propionate, or vehicle and were studied at weanling and adulthood. Different groups had distinct patterns of changes in tidal volume and frequency of breathing after aspartic acid administration. NR1 expression in hypothalamus was altered by age, sex, and treatment. Medullary and pontine NR1 expression correlated with baseline ventilation and magnitude of the ventilatory response to aspartic acid in some groups. Thus 1) tidal volume and breathing frequency patterns in response to aspartic acid are gender, age, and treatment dependent; 2) sex, age, and exogenous steroid hormones affect NR1 expression primarily in the hypothalamus; and 3) there is correlation between NR1 expression in pons and medulla with ventilatory parameters.