Diana / Spano Dopamine

1. Auflage 2014
ISBN: 978-0-444-63427-6
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, Band 211, 322 Seiten

Reihe: Progress in Brain Research

Progress in Brain Research is a well-established international series examining major areas of basic and clinical research within neuroscience, as well as emerging and promising subfields. This volume, concentrates on state-of-the-art of dopamine research: from basic science to clinical applications. It covers topics including thalamostriatal synapses as a substrate for dopamine action; the multilingual nature of dopamine neurons; ethanol-mechanisms along the mesolimbic dopamine system, and much more.Progress in Brain Research is the most acclaimed and accomplished series in neuroscience, firmly established as an extensive documentation of the advances in contemporary brain research. The volumes, some of which are derived from important international symposia, contain authoritative reviews and original articles by invited specialists. The rigorous editing of the volumes assures that they will appeal to all laboratory and clinical brain research workers in the various disciplines: neuroanatomy, neurophysiology, neuropharmacology, neuroendocrinology, neuropathology, basic neurology, biological psychiatry, and the behavioral sciences. - The most acclaimed and accomplished series in neuroscience - This volume looks at dopamine research in the light of the newest scholarly discoveries and insights

Autoren/Hrsg.

Diana, Marco

Spano, PierFranco

Leseproben

Chapter 1 Thalamostriatal synapses—another substrate for dopamine action?
Gordon W. Arbuthnott1    Brain Mechanisms for Behaviour Unit, OIST Graduate University, Onna-son, Kunigami-gun, Okinawa, Japan
1 Corresponding Author: Tel.: + 81-98-966-8402; Fax: + 81-98-966-8640 email address: [e-mail] Abstract
Over the years since the discovery of dopamine in the neostriatum, we have learned much about the anatomy of this large subcortical nucleus. In rodents, it is one nucleus penetrated by many fibers from the cerebral cortex. In larger animals and in humans, the area is split by a bundle of mainly corticofugal axons into the caudate nucleus and putamen. Dopamine input to both is similar and except for the details of cortical afferents to the two parts the striatum seems to act as one structure. Its main function is expected to be the transfer of the information carried in its cortical inputs onward through the basal ganglia. Diseases of this area of brain are associated with movement disorders and much is made of the action of dopamine on the long-term stability of corticostriatal synapses. The cortex is not at all the only input to the area, however, and the thalamus has almost as many synapses with striatal output neurons as has the cortex. This chapter summarizes the contributions to the study of the involvement of thalamostriatal inputs presented at Dopamine 2013 and emphasizes that this input, though largely ignored, has important lessons for those interested in understanding the function of the basal ganglia. Keywords corticostriatal thalamostriatal synapses spines striatal projection neurons striatal anatomy learned behavior Most introductions to the striatum start with the statement that all of the cerebral cortex is represented in the striatum, analyzed there, and passed on to the basal ganglia. The amazing focusing that this implies lends immediate interest to the striatal processing of cortical information. It is hardly surprising then that the cortical inputs to the striatum get such a lion's share of experimental interest. With the development of slices that preserve the cortical input to striatal cells (Arbuthnott et al., 1985; Kawaguchi et al., 1989), the study of the postsynaptic responses of striatal cells in vitro became popular. The other input to the striatum from the thalamus is much less studied. This chapter is a brief summary of some recent advances in the study of this important, but neglected, input to the basal ganglia system. 1 The “Other” Striatal Input
Already in their set of papers in “Proceedings of the Royal Society” Kemp and Powell (1971) described two sources of input to the striatum. Both ended on spines—or rather the elimination of both led to a loss of about half of the visible spines on the striatal densely spiny neurons. At the time, spiny neurons were considered to be the local interneurons of the striatum. We now know them to be projection neurons with axons leaving the nucleus for areas in the basal ganglia. Since then, the emphasis has been much more on the huge cortical input to the striatal complex, and the thalamic input has had relatively less influence. However, results from recent investigation of anatomical, physiological, behavioral, and clinical material all point to the importance of the thalamic input to striatum in normal behavior and in Parkinson's disease. We want to redress the balance by emphasizing recent additions to the literature that suggest that this input too is vital for the normal function of the basal ganglia. It is probably fair to say that the major change in the ability to study thalamostriatal terminals in detail, without the confusion of cortical terminals having similar endings on spines, was a consequence of the discovery that thalamic terminals can be identified by their use of vesicular glutamate transporter 2 (vGluT2) while cortical terminals express vGluT1 (Fremeau et al., 2001; Fujiyama et al., 2001; Herzog et al., 2001). That information first inspired me to try to study thalamic terminals specifically (Fig. 1) and it enabled the work of Bolam's group (Doig et al., 2010; Ellender et al., 2013) and Meredith's recent publication (Zhang et al., 2013). Figure 1 Thalamic terminals in striatum from an injection in Pf. The axons are stained with mCherry (red—bright in the printed version) and the animal was a BAC transgenic mouse with GFP driven from the D2 promoter so the green cells (pale gray in the printed version) are the indirect pathway SPNs and the black cells are the other SPNs. Even if the cortical input to striatum is the principal excitatory drive to the basal ganglia, it is apparent that the thalamus (mainly intralaminar nuclei) also provides a major excitatory innervation of the striatum. In quantitative terms, the thalamostriatal pathway gives rise to a similar number of synapses as does the corticostriatal pathway (Lacey et al., 2007; Raju et al., 2006) and equally innervates direct and indirect pathway spiny projection neurons (SPNs) (Doig et al., 2010). Thalamostriatal synapses have the same spatial relationship with dopaminergic axons and terminals as do corticostriatal synapses and are thus likely to be similarly modulated by dopamine (Moss and Bolam, 2008). Smeal (Smeal et al., 2007, 2008) and Ding (Ding et al., 2008) using similar slices of rodent brain illustrated differences between the two principal excitatory glutamatergic inputs to striatal SPNs arising from neurons in the cerebral cortex and thalamus. Using brain slices that allowed each type of synapse to be selectively activated, they started to reveal key elements of thalamostriatal synapse function, in direct comparison with cortical inputs. Although the two laboratories do not agree completely, there were differences in the excitatory postsynaptic potentials (EPSPs) derived from stimulation in thalamic reticular nucleus compared with direct stimulation of the overlying cortex. Such a scheme was open to other interpretation given that corticothalamic axons also connect with the reticular thalamus en route to the specific nuclei (Wright et al., 2000), while the thalamostriatal axons pass through the same area on the way to the striatum (Ding et al., 2008; Smeal et al., 2007, 2008). 2 Thalamostriatal Targets
Already an anatomical difference in the targets of the two striatal inputs had been suggested by work in the Anatomical Neuropharmacology Unit, Oxford. Lapper and Bolam (1992) described that the preponderance of the excitatory input to cholinergic giant aspiny interneurons came not from cortex but from thalamus. Although subsequent studies did demonstrate cortical input to these cholinergic cells (which was expected from the electrophysiology of the cells; Wilson et al., 1990a), the major input to the cell bodies comes from thalamus. Ding et al. (2010) found that activation of thalamostriatal axons from the parafascicular (Pf) nucleus, in a way that mimicked the response to salient stimuli, induced a burst of spikes in striatal cholinergic interneurons that was followed by a pause lasting more than half a second. This patterned interneuron activity triggered a transient, presynaptic suppression of cortical input to both major classes of principal SPNs that was followed by a prolonged enhancement of postsynaptic responsiveness in indirect pathway SPNs that are thought to control motor suppression. This differential regulation of the corticostriatal circuitry provides a neural substrate for attentional shifts and cessation of ongoing motor activity with the appearance of salient environmental stimuli. However, the thalamostriatal projection is highly heterogeneous. With combined electrophysiological and anatomical analyses, Lacey et al. (2007) have demonstrated that the properties of thalamostriatal neurons in the rostral intralaminar thalamus (central lateral nucleus, CL) are markedly different from those in the caudal intralaminar thalamus: Pf. Indeed, the distribution of Pf terminals seems to differ from all the other nuclei since they innervate dendritic shafts (including those of the cholinergic interneurons) more often than spines, whereas the opposite is true of the other intralaminar inputs (Raju et al., 2006; Wilson et al., 1990b). Furthermore, using an optogenetic approach, Ellender et al. (2013) have identified that CL and Pf synapses in the striatum have different functional properties. They conclude that the thalamostriatal projection possesses many characteristics in common with the corticostriatal projection, which is also highly heterogeneous (Wright et al., 1999). Thus, the major excitatory inputs to basal ganglia seem to be characterized by a marked heterogeneity in terminal fiber structure. The detailed understanding of the functional consequences of these terminal morphologies is hardly begun, but the first few experiments have been illuminating. Following on from the Lacey et al. (2007) study, Ellender et al. (2013) used an optogenetic approach to isolate and selectively activate thalamostriatal afferents arising in the CL or Pf thalamic nuclei individually and to study the properties of their synapses with principal spiny neurons recorded in vitro by patch...