Dopamine release is severely compromised in the R6/2 mouse model of Huntington's disease

• Published in: Journal of neurochemistry 2006-05, Vol.97 (3), p.737-746
• Main Authors: Johnson, Michael A, Rajan, Vignesh, Miller, Charles E, Wightman, R. Mark
• Format: Article
• Language: English
• Subjects: Age Factors; Animals; Biological and medical sciences; Cocaine; Cocaine - pharmacology; Corpus Striatum - drug effects; Corpus Striatum - metabolism; Degenerative and inherited degenerative diseases of the nervous system. Leukodystrophies. Prion diseases; Disease Models, Animal; dopamine; Dopamine - metabolism; Dopamine Uptake Inhibitors - pharmacology; Dose-Response Relationship, Drug; Electrochemistry - methods; huntingtin; Huntingtin Protein; Huntington Disease - genetics; Huntington Disease - metabolism; Huntington's disease; In Vitro Techniques; Medical sciences; Methamphetamine; Methamphetamine - pharmacology; Mice; Mice, Transgenic; Microelectrodes; Motor Activity - drug effects; Nerve Tissue Proteins - genetics; Nervous system (semeiology, syndromes); Nervous system as a whole; Neurological disorders; Neurology; Neurosciences; Neurotransmitters; Nuclear Proteins - genetics; Time Factors; voltammetry
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1111/j.1471-4159.2006.03762.x

Recently, alterations in dopamine signaling have been implicated in Huntington's disease. In this work, dopamine release and uptake was measured in striatal slices from the R6/2 transgenic mouse model of Huntington's disease using fast-scan cyclic voltammetry at carbon-fiber microelectrodes. Dopamine release in brain slices from 6-week-old R6/2 mice is substantially reduced (53% of wild type), while dopamine uptake is unaffected. In agreement with this, R6/2 mice injected with the dopamine uptake inhibitor cocaine exhibited a blunted motor activity response (54% of wild type). At 10 weeks of age, an even more dramatic motor activity decrease in response to cocaine injection (21% of wild type) was observed. Moreover, the pre-drug activity of 10-week-old R6/2 mice was significantly reduced (by 37%) compared with 6-week-old R6/2 mice. Striatal dopamine release decreased with age, indicating that progressive alterations in dopaminergic pathways may affect motor activity. The inhibition constants of cocaine and methamphetamine (METH) determined in brain slices differed little between genotype or age group, suggesting that the decreased responses to cocaine and METH arise from compromised dopamine release rather than differences in uptake or drug action. Collectively, these data demonstrate (i) a reduction in the ability of dopamine terminals to release dopamine and (ii) the importance of this attenuation of release on the motor symptoms of Huntington's disease.