The basomedial hypothalamus modulates the ventilatory response to hypoxia in neonatal rats.

We sought to examine the role of the basomedial hypothalamus in the regulation of breathing in neonatal rats. Small basomedial hypothalamic lesions were produced by a lesioning agent, goldthioglucose, in 5-d-old male rat pups, and 2 d later, baseline ventilation and the ventilatory responses to hypoxia and hypercapnia were examined. When compared with vehicle-injected controls, goldthioglucose-lesioned rat pups had a significantly slower respiratory rate and longer expiratory time at baseline. Lesioned rats displayed an impaired increase in breathing frequency in response to hypoxia, and augmented increases in tidal volume and respiratory drive (the ratio of tidal volume to inspiratory time) during hypoxia relative to controls. Hypercapnic responses were not affected. These data demonstrate that cells in a restricted area of the hypothalamus specifically influence the respiratory response to hypoxia.