CHANGES IN CATECHOLAMINE LEVELS AND TURNOVER RATES IN HYPOTHALAMIC, VOCAL CONTROL, AND AUDITORY NUCLEI IN MALE ZEBRA FINCHES DURING DEVELOPMENT

The catecholamines norepinephrine (NE) and dopamine (DA) have been imp licated in the sexual differentiation of brain and behavior and in spe cies-specific learning in several species. To determine if these neuro transmitters might-be involved in sexual differentiation of the vocal control system and song learning in male zebra finches, NE and DA leve ls and turnover rates were quantified in 10 behaviorally relevant brai n nuclei [6 vocal control (VCN), 2 auditory (AN), and 2 hypothalamic ( HN)I at four critical points during sexual differentiation of the VCN and the period of song learning, 25, 35, 55, and 90 days of age. Some birds were pretreated with alpha-methyl-para-tyrosine (alpha MPT) to a llow estimation of NE and DA turnover rates. NE and DA levels in micro dissected nuclei were quantified using high-performance liquid chromat ography with electrochemical detection. alpha MPT treatment suppressed catecholamine synthesis just as effectively in juveniles as it does i n adults and proved an effective method for estimating NE and DA turno ver rates. Patterns of NE and DA function in most VCN and AN over deve lopment were quite different from those in HN in which NE and DA funct ion changed gradually and showed no striking peaks. NE turnover rates changed significantly over development in all six VCN [nucleus interfa cialis (Nlf), high vocal center (HVC), nucleus robustus of the archist riatum (RA), dorsomedial portion of the intercollicular nucleus (DM), Area X of the parolfactory lobe, and lateral portion of the magnocellu lar nucleus of the anterior neostriatum (IMAN)]; one AN [nucleus mesen cephalicus lateralis pars dorsalis (MLd)], and one HN [preopticus ante rior (POA)]. NE levels changed significantly in two VCN (Nlf and Area X). In Nlf, RA, Area X, IMAN, and MLd, NE levels and/or turnover rates showed a striking peak at day 25, which was not seen in HN. Both DA l evels and turnover rates changed profoundly over development in 5 of 6 VCN (Nlf, RA, DM, Area X, and IMAN) and both AN (MLd and Field L). Th ese nuclei showed striking peaks in DA levels and turnover rates, prim arily on day 35 and/or 55, which then declined profoundly by day 90. T his contrasted with the minimal change in DA turnover rates seen in on e HN (POA) and the sixth VCN, HVC. In several VCN and AN, NE and DA le vels and turnover rates during development reached levels never seen i n adult males. Previous research has shown that catecholamine function is heightened in VCN during development compared to surrounding tissu es. Our data demonstrate that NE and DA function during development sh ows pronounced peaks in most VCN not seen in HN. This is interesting b ecause both VCN and HN are hormone sensitive, and both show hormone-mo dulated NE and DA function in adult males. The timing of these peaks s uggests that increased catecholaminergic function may be involved in s exual differentiation of the VCN and song learning in finches. (C) 199 8 John Wiley & Sons, Inc.