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 par t, upon CB cholinergic receptor stimulation. The aim of the present study w as to determine the role of cholinergic stimulation on DA release from rabb it pup CB with reference to adult's. CBs sampled from adult (n = 52) acid 1 0-day-old (n = 49) rabbits were incubated in vitro for 1 h in a surviving m edium 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 release d (DA,) in the medium was significantly larger with 1 muM carbachol compare d 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 co ntrol in 8% O-2 (P < 0.01). The data suggest that cholinergic mechanisms re gulating DA, are not fully expressed in pup rabbit CBs, in contrast with ad ults and thus, exhibit maturation-related functional differences. (C) 2001 Elsevier Science Ireland Ltd and the Japan Neuroscience Society. All rights reserved.