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

Abstract

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 μM 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 μM were studied. In adult CBs, domperidone increased DA r 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 μM ( P<0.01). In 10-day-old pup CBs, 1.0 μM 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.