Dopamine Dysregulation and Altered Responses to Drugs Affecting Dopaminergic Transmission in a New Dopamine Transporter Knockout (DAT-KO) Rat Model. (21st May 2022)

• Record Type: Journal Article
• Authors: Lloyd, Jordan T.; Yee, Andrew G.; Kalligappa, Prasanna K.; Jabed, Anower; Cheung, Pang Y.; Todd, Kathryn L.; Karunasinghe, Rashika N.; Vlajkovic, Srdjan M.; Freestone, Peter S.; Lipski, Janusz
• Is Part Of: Neuroscience. Volume 491(2022)
• Page Start: 43
• Page End: 64
• Publication Date: 2022-05-21
• Subjects: [DA]o extracellular dopamine concentration -- ACSF artificial cerebrospinal fluid -- CFM carbon fiber microelectrode -- CV coefficient of variation -- DA dopamine -- DAT dopamine transporter -- DAT-KO dopamine transporter knockout -- ELISA enzyme-linked immunosorbent assay -- FSCAV fast-scan controlled-adsorption voltammetry -- FSCV fast-scan cyclic voltammetry -- GIRK G protein-coupled inward rectifying K+ channels -- HET heterozygote -- L-DOPA 3, 4-dihydroxy-L-phenylalanine -- MAO monoamine oxidase -- MFB medial forebrain bundle -- MT medial terminal nucleus of the accessory optic tract -- OCT3 organic cation transporter 3 -- SNc substantia nigra pars compacta -- TH tyrosine hydroxylase -- WT wild-type -- αMPT alpha-methyl-p-tyrosine; dopamine transporter -- CRISPR/Cas9 -- electrochemistry -- electrophysiology -- brain slice -- in vivo; Neurochemistry -- Periodicals; Neurophysiology -- Periodicals; Neurology -- Periodicals; Neurochimie -- Périodiques; Neurophysiologie -- Périodiques; Neurochemistry; Neurophysiology; Electronic journals; Periodicals; Electronic journals; 612.8
• DOI: 10.1016/j.neuroscience.2022.03.019
• Languages: English
• ISSNs: 0306-4522

Abstract

Highlights: Our genetic model extends the range of animals for dopamine dysregulation studies. Voltammetry was used to measure dopamine both in the striatum and substantia nigra. Genetic DAT inactivation enhances electrically-stimulated dopamine overflow. MAO greatly contributes to dopamine clearance after L-DOPA-induced release. OCT3 contributes to DA clearance in dorsal striatum after genetic DAT inactivation. Abstract: Under normal conditions, dopamine (DA) clearance after release largely depends on uptake by the DA transporter (DAT). DAT expression/activity is reduced in some neuropsychiatric and neurological disorders. Our aim was to characterize the behavioral, neurochemical and electrophysiological effects of eliminating DAT in a novel knockout rat model we generated using CRISPR/Cas9. Consistent with existing DAT-KO models, our DAT-KO rats displayed increased locomotion, paradoxical calming by amphetamine, and reduced kinetics of DA clearance after stimulated release. Reduced DA kinetics were demonstrated using fast-scan cyclic voltammetry in brain slices containing the striatum or substantia nigra pars compacta (SNc) and in the dorsal striatum in vivo . Cocaine enhanced DA release in wild-type (WT) but not DAT-KO rats. Basal extracellular DA concentration measured with fast-scan controlled-adsorption voltammetry was higher in DAT-KO rats both in the striatum and SNc and was enhanced by L-DOPA (particularly after pharmacological block of monoamine oxidase), confirming that DA release after L-DOPA is not due to DAT reversal. The baseline firing frequency of SNc neurons was similar in both genotypes. However, D2 receptor-mediated inhibition of firing (by quinpirole or L-DOPA) was blunted in DAT-KO rats, while GABAB -mediated inhibition was preserved. We have also provided new data for the DAT-KO rat regarding the effects of slowing DA diffusion with dextran and blocking organic cation transporter 3 with corticosterone. Together, our results validate our DAT-KO rat and provide new insights into the mechanisms of chronic dysregulation of the DA system by addressing several unresolved issues in previous studies with other DAT-KO models.