Carbachol effect on carotid body dopamine in vitro release in response to hypoxia in adult and pup rabbit

Dopamine (DA) release from the adult carotid body (CB) is dependent, in part, upon CB cholinergic receptor stimulation. The aim of the present study was to determine the role of cholinergic stimulation on DA release from rabbit pup CB with reference to adult's. CBs sampled from adult (n = 52) acid 10-day-old (n = 49) rabbits were incubated in vitro for 1 h in a surviving medium bubbled with either 100 or 8% O-2 in N-2, without (control) or in the presence of the cholinergic agonist carbachol 1 muM. In adults, DA released (DA,) in the medium was significantly larger with 1 muM carbachol compared with control in either 100 or 8% O-2 (P < 0.01). In pups, carbachol 1 muM had no effect in 100% O-2 but significantly increased DA, compared with control in 8% O-2 (P < 0.01). The data suggest that cholinergic mechanisms regulating DA, are not fully expressed in pup rabbit CBs, in contrast with adults and thus, exhibit maturation-related functional differences. (C) 2001 Elsevier Science Ireland Ltd and the Japan Neuroscience Society. All rights reserved.