title: Cocaine inhibits NGF-induced PC12 cells differentiation through D(1)-type dopamine receptors.
abstract: In utero cocaine exposure can adversely affect CNS development. Previous studies showed that cocaine inhibits neuronal differentiation in a dose-dependent fashion in nerve growth factor (NGF)-stimulated PC12 cells. Cocaine binds with high affinity to several neurotransmitter transporters, resulting in elevated neurotransmitter levels in nerve endings. To determine if cocaine inhibits neurite outgrowth through the effects of these neurotransmitters, we applied dopamine, norepinephrine, serotonin, and acetylcholine to NGF-induced PC12 cells. Dopamine was the only neurotransmitter to inhibit neurite outgrowth significantly in a dose-dependent pattern without affecting cell viability. Norepinephrine and acetylcholine did not affect neurite outgrowth, while serotonin enhanced it. Furthermore, GBR 12909, a potent dopamine transporter (DAT) inhibitor, yielded similar effects. We then showed PC12 cells express D(1) and D(2) receptors and DAT proteins. Dopamine uptake measured over time was significantly blocked by cocaine and GBR 12909 which may result in elevated extracellular dopamine. The role of dopamine receptors in PC12 differentiation was further examined by using D(1) and D(2) specific receptor agonists. Only the D(1) agonist, SKF-38393, had a significant dose-dependent inhibitory effect. In addition, a D(1) antagonist produced significant recovery of neurite outgrowth in cocaine-treated cells. These findings suggest that cocaine inhibitory effects on neuronal differentiation are mediated through its binding to the dopamine transporter, resulting in increased dopamine level in the synapses. Subsequently, up regulation of D(1) receptors alters NGF signaling pathways.
authors.affiliation: Department of Pediatrics, University of Alabama at Birmingham, 331C, Sparks Building, 1720 Seventh Avenue South, Birmingham, AL 35294-0017, USA. dzachor@civmail.circ.uab.edu
authors.forename: D A
authors.initials: DA
authors.lastname: Zachor
authors.forename: J F
authors.initials: JF
authors.lastname: Moore
authors.forename: C
authors.initials: C
authors.lastname: Brezausek
authors.forename: A
authors.initials: A
authors.lastname: Theibert
authors.forename: A K
authors.initials: AK
authors.lastname: Percy
mesh_terms: D000818:Animals; D001921:Brain / Q000166:cytology / Q000187:drug effects* / Q000196:embryology; D002352:Carrier Proteins / Q000187:drug effects / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects* / Q000502:physiology; D003042:Cocaine / Q000633:toxicity*; D004298:Dopamine / Q000378:metabolism; D065127:Dopamine D2 Receptor Antagonists; D050483:Dopamine Plasma Membrane Transport Proteins; D018765:Dopamine Uptake Inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005314:Embryonic and Fetal Development / Q000187:drug effects / Q000502:physiology; D005260:Female; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D020932:Nerve Growth Factor / Q000378:metabolism / Q000494:pharmacology*; D009419:Nerve Tissue Proteins; D016501:Neurites / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D018377:Neurotransmitter Agents / Q000378:metabolism / Q000494:pharmacology; D016716:PC12 Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D010879:Piperazines / Q000494:pharmacology; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D051381:Rats; D017447:Receptors, Dopamine D1 / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism; D017448:Receptors, Dopamine D2 / Q000819:agonists / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D065127:Dopamine D2 Receptor Antagonists; D050483:Dopamine Plasma Membrane Transport Proteins; D018765:Dopamine Uptake Inhibitors; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D018377:Neurotransmitter Agents; D010879:Piperazines; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; C493216:Slc6a3 protein, rat; D020932:Nerve Growth Factor; C043425:vanoxerine; D003042:Cocaine; D004298:Dopamine