Effects of vagotomy and glossopharyngectomy on respiratory response to dopamine-agonists.

In normal rats lightly anesthetized with halothane apomorphine increased both resting and CO2-dependent minute ventilation (VM) by stimulating respiratory frequency (RF) whereas tidal volume (VT) was slightly decreased. Acute bilateral glossopharyngectomy, which impaired carotid body function, did not change the apomorphine effects in contrast to bilateral vagotomy, which abolished the RF response of the drug, but now increased VT. Intravenous infusion of dopamine increased VM by elevating RF, and this effect was only slightly blunted by bilateral glossopharyngectomy but nearly abolished by vagotomy and totally eliminated by the combined procedures. The respiratory response to dopamine was depressed in rats with chronically destroyed central catecholaminergic neurons. These findings indicate that there may be two different dopaminergic stimulatory mechanisms that modulate RF-one peripheral and one central-and both depend upon afferent vagal activity. With impaired vagal function, however, two other dopaminergic stimulatory mechanisms effecting VT are evident-one central, and one peripheral which involves the carotid body.