DEVELOPING SYMPATHETIC NEURONS EXPRESS A NEURONAL TRAIT BEFORE A CATECHOLAMINERGIC SYNTHETIC ENZYME IN-VIVO

How multiple mature phenotypic traits are regulated in developing neur ons remains a central problem in developmental neurobiology, Mature sy mpathetic neurons express general neuronal epitopes, including neuron specific tubulin (NST) as well as markers involved in neurotransmitter synthesis including tyrosine hydroxylase (TH), To investigate the rel ationship between neuronal differentiation and neurotransmitter develo pment, the order of appearance of NST and TH was determined in both ch ick and rat embryonic sympathetic ganglia by double-label immunohistoc hemistry, In differentiated ganglia, these two markers were expressed in virtually all sympathetic neurons examined, By contrast, at early s tages of embryonic development in both chick and rat, sympathetic gang lia contained many NST immunoreactive (IR) cells, but few precursors w ere TH-IR, With further development, more NST-IR cells were also TH-IR , and these two markers gradually became coexpressed with subsequent d evelopment, These data provide evidence that general neuronal and neur otransmitter differentiation events are separable and independently re gulated during cellular diversification in the adrenergic lineage. (C) 1996 Wiley-Liss, Inc.