Autoreceptor mechanism regulating carotid body dopamine release from adult and 10-day-old rabbits

Dopamine (DA) release (r) from the carotid body (CB) is thought to be modulated by feedback inhibition mediated by DA D-2 autoreceptors, We tested the hypothesis that CB DA(r) is autoregulated in a concentration and age dependent manner. Using an in vitro CB infusion model [Bairam, A., Marchal, F., Cottet-Emard, J.M., Basson, H., Pequignot, J.M., Hascoet, J.M., Lahiri, S., 1996b. Effects of hypoxia on carotid body dopamine content and release in developing rabbits. J. Appl. Physiol. 80, 20-24.], we evaluated under unstimulated conditions the effects of 0.001, 0.01. 0.1, 1.0 and 10.0 mu M of the specific DA D-2 receptor antagonist domperidone on CB DA(r) in adult rabbits, in 10-day-old rabbit pups, concentrations of 0.01, 0.1, 1.0 mu M were studied. In adult CBs, domperidone increased DA, in a concentration-dependent manner. DA(r) (pmol/h) was significantly greater compared to control (without domperidone) starting at a domperidone concentration of 0.1 mu M (P<0.01). In 10-day-old pup CBs, 1.0 mu M domperidone was required to produce a significant increase of DA(r) (pmol/h) compared to control (P<0.005). However, control DA(r) (as % of total catecholamine) was about 40%: significantly higher than 24% observed in adult CBs (P<0.001). We conclude that in rabbit CB. DA(r) is controlled by an autoreceptor mechanism in a concentration-dependent manner and this mechanism is less developed in pups than in adults. (C) 2000 Elsevier Science B.V. All rights reserved.