Dopamine-induced ventilatory depression in the rat, mediated by carotid nerve afferents

In pentobarbitone-anesthetized rats, i.v. injections of dopamine (DA) at (10-8)-(10-5 g/kg led to transient ventilatory depression, usually not associated with changes in systemic arterial pressure. DA-induced ventilatory depression consisted of decreases in tidal volume and respiratory frequency in 12 rats, and in bradypnea without changes in tidal volume in 5 rats. After bilateral section of the carotid nerves, ventilatory responses to DA were abolished or greatly diminished. It is concluded that DA inhibits carotid body chemosensory discharges in the rat. The possibility that chemosensory activity directly affects respiratory frequency is discussed.