title: Dependence of serotonergic and other nonadrenergic enteric neurons on norepinephrine transporter expression.
abstract: The norepinephrine transporter (NET), which is expressed on the plasma membranes of noradrenergic neurons, is important in terminating neurotransmission. The noradrenergic sympathetic neurons that innervate the bowel express NET, but they are extrinsic and their cell bodies are not components of the enteric nervous system (ENS). Subsets of neurons were nevertheless found in the murine ENS that express transcripts encoding NET, NET protein, and dopamine β-hydroxylase; these neurons lack tyrosine hydroxylase (TH) and thus are not catecholaminergic. Enteric NET expression, moreover, preceded the ingrowth of sympathetic axons during development and did not disappear when the gut was extrinsically denervated. Transiently catecholaminergic (TC), neural crest-derived precursors of enteric neurons expressed NET at embryonic day 10 (E10) and NET expression in the fetal gut peaked coincidentally with early neurogenesis at E12. Serotonergic neurons, which are born early from TC progenitors, were found to express NET in the adult ENS, as did also other early-born neurons containing calretinin or neuronal nitric oxide synthase (nNOS) immunoreactivities. NET was not expressed in TH-immunoreactive dopaminergic neurons, which are born perinatally. Genetic deletion of NET almost eliminated tryptophan hydroxylase 2 expression and significantly reduced the numbers of total, 5-HT- and calretinin-immunoreactive enteric neurons, without affecting the immunoreactivities of nNOS or TH. These observations indicate that TC precursors of subsets of noncatecholaminergic enteric neurons express NET that persists in the successors of these cells despite their loss of TH. NET expression is essential for development and/or survival of some (5-HT- and calretinin-expressing), but not all (nNOS-expressing), of these neurons.
authors.affiliation: Department of Pathology and Cell Biology, Columbia University, New York, New York 10032, USA. ZL64@columbia.edu
authors.forename: Zhishan
authors.initials: Z
authors.lastname: Li
authors.forename: Marc G
authors.initials: MG
authors.lastname: Caron
authors.forename: Randy D
authors.initials: RD
authors.lastname: Blakely
authors.forename: Kara G
authors.initials: KG
authors.lastname: Margolis
authors.forename: Michael D
authors.initials: MD
authors.lastname: Gershon
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D017763:Autonomic Denervation / Q000379:methods; D050483:Dopamine Plasma Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D004622:Embryo, Mammalian; D017615:Enteric Nervous System / Q000166:cytology* / Q000196:embryology / Q000254:growth & development; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009474:Neurons / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism; D009638:Norepinephrine / Q000378:metabolism*; D050484:Norepinephrine Plasma Membrane Transport Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism*; D014365:Tryptophan Hydroxylase / Q000235:genetics / Q000378:metabolism; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
chemical_list: D050483:Dopamine Plasma Membrane Transport Proteins; D050484:Norepinephrine Plasma Membrane Transport Proteins; D012701:Serotonin; D052248:Nitric Oxide Synthase Type I; D014446:Tyrosine 3-Monooxygenase; C487802:Tph2 protein, mouse; D014365:Tryptophan Hydroxylase; D009638:Norepinephrine