Present address: Medical Research Council Anatomical Neuropharmacology Unit, University of Oxford, Mansfield Road, Oxford OX1 3TH, UK.
Exclusive and common targets of neostriatofugal projections of rat striosome neurons: a single neuron-tracing study using a viral vector
Article first published online: 14 FEB 2011
© 2011 The Authors. European Journal of Neuroscience © 2011 Federation of European Neuroscience Societies and Blackwell Publishing Ltd
European Journal of Neuroscience
Volume 33, Issue 4, pages 668–677, February 2011
How to Cite
Fujiyama, F., Sohn, J., Nakano, T., Furuta, T., Nakamura, K. C., Matsuda, W. and Kaneko, T. (2011), Exclusive and common targets of neostriatofugal projections of rat striosome neurons: a single neuron-tracing study using a viral vector. European Journal of Neuroscience, 33: 668–677. doi: 10.1111/j.1460-9568.2010.07564.x
- Issue published online: 14 FEB 2011
- Article first published online: 14 FEB 2011
- Received 9 August 2010, revised 24 September 2010, accepted 16 November 2010
- reinforcement learning;
- single neuron labeling;
- striosome compartment;
- viral vector
The rat neostriatum has a mosaic organization composed of striosome/patch compartments embedded in a more extensive matrix compartment, which are distinguished from each other by the input–output organization as well as by the expression of many molecular markers. The matrix compartment gives rise to the dual γ-aminobutyric acid (GABA)ergic striatofugal systems, i.e. direct and indirect pathway neurons, whereas the striosome compartment is considered to involve direct pathway neurons alone. Although the whole axonal arborization of matrix striatofugal neurons has been examined in vivo by intracellular staining, that of striosome neurons has never been studied at the single neuron level. In the present study, the axonal arborizations of single striosome projection neurons in rat neostriatum were visualized in their entirety using a viral vector expressing membrane-targeted green fluorescent protein, and compared with that of matrix projection neurons. We found that not only matrix but also striosome compartments contained direct and indirect pathway neurons. Furthermore, only striatonigral neurons in the striosome compartment projected directly to the substantia nigra pars compacta (SNc), although they sent a substantial number of axon collaterals to the globus pallidus, entopeduncular nucleus and/or substantia nigra pars reticulata. These results suggest that striosome neurons play a more important role in the formation of reward-related signals of SNc dopaminergic neurons than do matrix neurons. Together with data from previous studies in the reinforcement learning theory, our results suggest that these direct and indirect striosome–SNc pathways together with nigrostriatal dopaminergic neurons may help striosome neurons to acquire the state-value function.