NEUROTROPHIN-3-MEDIATED AND NOREPINEPHRINE-MEDIATED ADRENERGIC-DIFFERENTIATION AND THE INHIBITORY-ACTION OF DESIPRAMINE AND COCAINE

In the presence of neurotrophin-3 (NT-3), high-affinity norepinephrine (NE) uptake by quail neural crest cells was significantly increased a s judged by in vitro colony assay of adrenergic differentiation. In th e presence of the related neurotrophins nerve growth factor (NGF) or b rain-derived neurotrophic (BDNF) factor, or of basic fibroblast growth factor (bFGF), there were no significant changes. When NE was added t o the culture medium in addition to NT-3, more colonies contained dopa mine-beta-hydroxylase (DBH)-immunoreactive cells, an enzyme that is ch aracteristic for adrenergic cells. The NE-mediated increase in the por tion of colonies that contained DBH-immunoreactive cells was prevented by the tricyclic antidepressant desipramine (DMI) and by cocaine, two types of drug that block cellular transport of NE, To further examine whether NE acts via uptake, colony assays were performed in the prese nce and absence of adrenergic antagonists and agonists. These would be expected to mimic the DMI and NE effects, respectively, if the mechan ism of action involved activation of adrenergic autoreceptors. Neither class of drug showed a detectable effect within a wide range of conce ntrations. Immunocytochemistry using antibodies against beta 1 and bet a 2 adrenergic receptors further supported the notion that DMI action and beta-receptor expression are not causally related. Ratio imaging w as subsequently used in an attempt to elucidate the mechanism of NE ac tion. Within a few minutes of addition of NE to the culture medium, th ere was an increase in intracellular free calcium in a subset of neura l crest cells. Taken together, our data indicate that NT-3 Is involved in the appearance of the NE transporter (NET) during embryonic develo pment; internalized NE directly or indirectly increases adrenergic dif ferentiation as measured by immunoreactivity of the adrenergic biosynt hetic enzyme DBH; and norepinephrine uptake inhibitors have teratogeni c potential. (C) 1997 John Wiley & Sons, Inc.