Dual responses of carotid chemosensory afferents to dopamine in the newborn kitten

The effects of dopamine and of dopamine D2 receptor blocker haloperidol on the activity of carotid chemoreceptors were studied in 24 anesthetized, paralyzed and artificially ventilated newborn kittens aged 0–17 days. Single or few fiber preparations of chemoreceptors were made from one carotid sinus nerve. The responses of the chemosensory afferents to intravenous injections of dopamine (5–50 μg·kg −1) were studied in kittens breathing air and 8% O 2 in N 2. The effects of haloperidol on the chemosensory activity in air or 100% O 2 and on the chemosensory response to hypoxia were studied. Dopamine inhibited the chemosensory discharge in 25 44 studies in normoxia. Of the 9 studies performed in hypoxia, dopamine was excitatory in 5 or had no effect in 4 ( P