Mice expressing markedly reduced striatal dopamine transporters exhibit increased locomotor activity, dopamine uptake turnover rate, and cocaine responsiveness
Article first published online: 30 MAY 2013
Copyright © 2013 Wiley Periodicals, Inc.
Volume 67, Issue 10, pages 668–677, October 2013
How to Cite
Rao, A., Sorkin, A. and Zahniser, N. R. (2013), Mice expressing markedly reduced striatal dopamine transporters exhibit increased locomotor activity, dopamine uptake turnover rate, and cocaine responsiveness. Synapse, 67: 668–677. doi: 10.1002/syn.21671
- Issue published online: 23 AUG 2013
- Article first published online: 30 MAY 2013
- Accepted manuscript online: 8 APR 2013 04:21AM EST
- Manuscript Accepted: 23 MAR 2013
- Manuscript Received: 4 DEC 2012
- NIH. Grant Numbers: R01 DA004216, R01 DA014204, K05 DA015050, F32 DA029357
- neurotransmitter transporter;
- mouse model;
- [3H]WIN 35,428
Variations in the expression levels of the dopamine transporter (DAT) can influence responsiveness to psychostimulant drugs like cocaine. To better understand this relationship, we studied a new DAT-low expresser (DAT-LE) mouse model and performed behavioral and biochemical studies with it. Immunoblotting and [3H]WIN 35,428 binding analyses revealed that these mice express ∼35% of wildtype (WT) mouse striatal DAT levels. Compared to WT mice, DAT-LE mice were hyperactive in a novel open-field environment. Despite their higher basal locomotor activity, cocaine (10 or 20 mg/kg, i.p.) induced greater locomotor activation in DAT-LE mice than in WT mice. The maximal velocity (Vmax) of DAT-mediated [3H]DA uptake into striatal synaptosomes was reduced by 46% in DAT-LE mice, as compared to WT. Overall, considering the reduced number of DAT binding sites (Bmax) along with the reduced Vmax in DAT-LE mice, a 2-fold increase in DA uptake turnover rate (Vmax/Bmax) was found, relative to WT mice. This suggests that neuroadaptive changes have occurred in the DAT-LE mice that would help to compensate for their low DAT numbers. Interestingly, these changes do not include a reduction in tyrosine hydroxylase levels, as was previously reported in DAT knockout homozygous and heterozygous animals. Further, these changes are not sufficient to prevent elevated novelty- and cocaine-induced locomotor activity. Hence, these mice represent a unique model for studying changes of in vivo DAT function and regulation that result from markedly reduced levels of DAT expression. Synapse 67:668–677, 2013. © 2013 Wiley Periodicals, Inc.