We hypothesized that administration of estradiol benzoate (EB) to males and testosterone propionate (TP) to female neonatal rat pups, alters gender-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 EB, TP, or vehicle and studied at weanling and adulthood. Different groups had distinct patterns of changes in tidal volume (V_T) and frequency of breathing (f) after aspartic acid administration. NR1 expression in hypothalamus was altered by age, gender, and treatment. Medullary and pontine NR1 expression correlated with baseline ventilation and the magnitude of the ventilatory response to aspartic acid in some groups. Thus, 1) V_T and f patterns in response to aspartic acid are gender, age and treatment dependent; 2) gender, 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.