Effects of GABAA receptor antagonism on inspiratory activities in kittens

In anesthetized kittens (< 1 to 24 days old), the effects of GABAA receptor antagonism on phrenic, hypoglossal and cervical sympathetic discharges were examined by i.v. bicuculline infusions during hyperoxia and hypoxia. Administration of bicuculline during hyperoxia produced marked increases in the amplitudes of inspiratory nerve discharges. During hypoxic stimulation (10% O2), the amplitudes of inspiratory activities decreased towards or below those observed during hyperoxia; bicuculline reversed this depression and restored inspiratory discharges. Our results indicated that GABAA receptors were functional shortly after birth, acting to mediate influences shaping inspiratory activity during hyperoxic breathing and during conditions of increased chemical drive.