title: Chronic desipramine treatment alters tyrosine hydroxylase but not norepinephrine transporter immunoreactivity in norepinephrine axons in the rat prefrontal cortex.
abstract: Pharmacological blockade of norepinephrine (NE) reuptake is clinically effective in treating several mental disorders. Drugs that bind to the NE transporter (NET) alter both protein levels and activity of NET and also the catecholamine synthetic enzyme tyrosine hydroxylase (TH). We examined the rat prefrontal cortex (PFC) by electron microscopy to determine whether the density and subcellular distribution of immunolabelling for NET and co-localization of NET with TH within individual NE axons were altered by chronic treatment with the selective NE uptake inhibitor desipramine (DMI). Following DMI treatment (21 d, 15 mg/kg.d), NET-immunoreactive (ir) axons were significantly less likely to co-localize TH. This finding is consistent with reports of reduced TH levels and activity in the locus coeruleus after chronic DMI and indicates a reduction of NE synthetic capacity in the PFC. Measures of NET expression and membrane localization, including the number of NET-ir profiles per tissue area sampled, the number of gold particles per NET-ir profile area, and the proportion of gold particles associated with the plasma membrane, were similar in DMI- and vehicle-treated rats. These findings were verified using two different antibodies directed against distinct epitopes of the NET protein. The results suggest that chronic DMI treatment does not reduce NET expression within individual NE axons in vivo or induce an overall translocation of NET protein away from the plasma membrane in the PFC as measured by ultrastructural immunogold labelling. Our findings encourage consideration of possible post-translational mechanisms for regulating NET activity in antidepressant-induced modulation of NE clearance.
authors.affiliation: Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA.
authors.forename: Susan L
authors.initials: SL
authors.lastname: Erickson
authors.forename: Anjalika R
authors.initials: AR
authors.lastname: Gandhi
authors.forename: Josephine K
authors.initials: JK
authors.lastname: Asafu-Adjei
authors.forename: Allan R
authors.initials: AR
authors.lastname: Sampson
authors.forename: LeeAnn
authors.initials: L
authors.lastname: Miner
authors.forename: Randy D
authors.initials: RD
authors.lastname: Blakely
authors.forename: Susan R
authors.initials: SR
authors.lastname: Sesack
mesh_terms: D059331:Adrenergic Neurons / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D018759:Adrenergic Uptake Inhibitors / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D000818:Animals; D000929:Antidepressive Agents, Tricyclic / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology; D001369:Axons / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D003891:Desipramine / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D007150:Immunohistochemistry; D015918:Infusion Pumps, Implantable; D008297:Male; D046529:Microscopy, Electron, Transmission; D009419:Nerve Tissue Proteins / Q000378:metabolism; D050484:Norepinephrine Plasma Membrane Transport Proteins / Q000378:metabolism*; D017397:Prefrontal Cortex / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D013570:Synaptic Membranes / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism*
chemical_list: D018759:Adrenergic Uptake Inhibitors; D000929:Antidepressive Agents, Tricyclic; D009419:Nerve Tissue Proteins; D050484:Norepinephrine Plasma Membrane Transport Proteins; C493226:Slc6a2 protein, rat; D014446:Tyrosine 3-Monooxygenase; D003891:Desipramine