Ablation of kappa-opioid receptors from brain dopamine neurons has anxiolytic-like effects and enhances cocaine-induced plasticity

Ashlee Van'T Veer, Anita J. Bechtholt, Sara Onvani, David Potter, Yujun Wang, Lee Yuan Liu-Chen, Günther Schütz, Elena H. Chartoff, Uwe Rudolph, Bruce M. Cohen, William A. Carlezon

Research output: Contribution to journalArticlepeer-review

Abstract

Brain kappa-opioid receptors (KORs) are implicated in states of motivation and emotion. Activation of KORs negatively regulates mesolimbic dopamine (DA) neurons, and KOR agonists produce depressive-like behavioral effects. To further evaluate how KOR function affects behavior, we developed mutant mice in which exon 3 of the KOR gene (Oprk1) was flanked with Cre-lox recombination (loxP) sites. By breeding these mice with lines that express Cre-recombinase (Cre) in early embryogenesis (EIIa-Cre) or only in DA neurons (dopamine transporter (DAT)-Cre), we developed constitutive KOR knockouts (KOR-/-) and conditional knockouts that lack KORs in DA-containing neurons (DAT-KOR lox/lox). Autoradiography demonstrated complete ablation of KOR binding in the KOR-/- mutants, and reduced binding in the DAT-KORlox/lox mutants. Quantitative reverse transcription PCR (qPCR) studies confirmed that KOR mRNA is undetectable in the constitutive mutants and reduced in the midbrain DA systems of the conditional mutants. Behavioral characterization demonstrated that these mutant lines do not differ from controls in metrics, including hearing, vision, weight, and locomotor activity. Whereas KOR-/- mice appeared normal in the open field and light/dark box tests, DAT-KORlox/lox mice showed reduced anxiety-like behavior, an effect that is broadly consistent with previously reported effects of KOR antagonists. Sensitization to the locomotor-stimulating effects of cocaine appeared normal in KOR-/- mutants, but was exaggerated in DAT-KORlox/lox mutants. Increased sensitivity to cocaine in the DAT-KOR lox/lox mutants is consistent with a role for KORs in negative regulation of DA function, whereas the lack of differences in the KOR -/- mutants suggests compensatory adaptations after constitutive receptor ablation. These mouse lines may be useful in future studies of KOR function.

Original languageEnglish (US)
Pages (from-to)1585-1597
Number of pages13
JournalNeuropsychopharmacology
Volume38
Issue number8
DOIs
StatePublished - Jul 2013
Externally publishedYes

Keywords

  • anxiety
  • cocaine.
  • dopamine
  • kappa-opioid receptor
  • mutation

ASJC Scopus subject areas

  • Pharmacology
  • Psychiatry and Mental health

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