Regulators of G protein signaling (RGS) modulate heterotrimeric G proteins in part by serving as GTPase-activating proteins for Galpha subunits. We examined a role for RGS9-2, an RGS subtype highly enriched in striatum, in modulating dopamine D2 receptor function. Viral-mediated overexpression of RGS9-2 in rat nucleus accumbens (ventral striatum) reduced locomotor responses to cocaine (an indirect dopamine agonist) and to D2 but not to D1 receptor agonists. Conversely, RGS9 knockout mice showed heightened locomotor and rewarding responses to cocaine and related psychostimulants. In vitro expression of RGS9-2 in Xenopus oocytes accelerated the off-kinetics of D2 receptor-induced GIRK currents, consistent with the in vivo data. Finally, chronic cocaine exposure increased RGS9-2 levels in nucleus accumbens. Together, these data demonstrate a functional interaction between RGS9-2 and D2 receptor signaling and the behavioral actions of psychostimulants and suggest that psychostimulant induction of RGS9-2 represents a compensatory adaptation that diminishes drug responsiveness.

No abstract

Knock-in mice were generated that harbored a leucine-to-serine mutation in the ␣4 nicotinic receptor near the gate in the channel pore. Mice with intact expression of this hypersensitive receptor display dominant neonatal lethality. These mice have a severe deficit of dopaminergic neurons in the substantia nigra, possibly because the hypersensitive receptors are continuously activated by normal extracellular choline concentrations. A strain that retains the neo selection cassette in an intron has reduced expression of the hypersensitive receptor and is viable and fertile. The viable mice display increased anxiety, poor motor learning, excessive ambulation that is eliminated by very low levels of nicotine, and a reduction of nigrostriatal dopaminergic function upon aging. These knock-in mice provide useful insights into the pathophysiology of sustained nicotinic receptor activation and may provide a model for Parkinson's disease.T he mechanism leading from nicotine intake to addiction is not known in detail, but it begins with the activation of neuronal nicotinic acetylcholine receptors (nAChRs). Nicotine elicits dopamine release in several regions of the brain, presumably leading to the reward, motor, and addictive effects (1, 2). The highest-affinity and most abundant nicotine binding in the brain corresponds to the ␣4␤2 nAChR (3). The ␣4 subunit is the principal partner for the ␤2 subunit in brain; ␤2-containing receptors play an important role in nicotine self-administration, in nicotine-stimulated electrophysiological responses in midbrain neurons, and in nicotine-stimulated dopamine release in the ventral striatum (4, 5). The ␣4 subunit and tyrosine hydroxylase are colocalized in dopaminergic neurons (6). Epidemiological studies show that smokers have a lower incidence of Parkinson's disease (7,8), suggesting a protective effect of nicotine via modulation of the dopaminergic system. Both ␣4 and ␤2 knockout mice show only subtle alterations in their physiology or behavior until they reach old age (4, 9, 10). We have used a complementary strategy to understand the roles of ␣4-containing nAChRs. We reasoned that gain of function mutations might generate more noticeable phenotypes, and that these phenotypes would gain relevance from the fact that nicotine and some candidate analgesics (11) are agonists. We have generated lines of knock-in mice by introducing a point mutation into the M2 transmembrane region of the ␣4 subunit to produce a hypersensitive receptor. Materials and MethodsXenopus Oocyte Injections and Electrophysiology. The ␣4 and ␤2 subunits were subcloned into pAMV-PA (12). Capped mRNA transcripts were prepared, and ␣4͞␤2 (2 ng, 1:1) or ␣4L9ЈS͞␤2 (0.2-0.5 ng, 1:1) were microinjected into Xenopus oocytes (12). Twenty-four to seventy-two hours later, two-electrode voltage clamp recordings (12) were made in solutions containing zero Ca 2ϩ .Knock-in Mouse Construction. A 129͞SvJ ␣4 genomic clone containing exon 5 and the L9ЈS mutation was inserted into pKO Scrambler V907 (Lexicon-Genetics, The Woodland...

Regulator of G-protein signaling 9-2 (RGS9-2), a member of the RGS family of G␣ GTPase accelerating proteins, is expressed specifically in the striatum, which participates in antipsychotic-induced tardive dyskinesia and in levodopa-induced dyskinesia. We report that RGS9 knock-out mice develop abnormal involuntary movements when inhibition of dopaminergic transmission is followed by activation of D 2 -like dopamine receptors (DRs). These abnormal movements resemble drug-induced dyskinesia more closely than other rodent models. Recordings from striatal neurons of these mice establish that activation of D 2 -like DRs abnormally inhibits glutamate-elicited currents. We show that RGS9-2, via its DEP domain (for Disheveled, EGL-10, Pleckstrin homology), colocalizes with D 2 DRs when coexpressed in mammalian cells. Recordings from oocytes coexpressing D 2 DR or the m2 muscarinic receptor and G-protein-gated inward rectifier potassium channels show that RGS9-2, via its DEP domain, preferentially accelerates the termination of D 2 DR signals. Thus, alterations in RGS9-2 may be a key factor in the pathway leading from D 2 DRs to the side effects associated with the treatment both of psychoses and Parkinson's disease.

No abstract

The efficient generation of specific brain cells in vitro may serve as a source of cells for brain repair in several devastating neurological diseases. Production of dopaminergic neurons from precursor cells for transplantation in Parkinson's disease has become a major research goal. We found that murine mesencephalic neurospheres were viable and proliferated, preserved telomerase activity, pluripotency and dopaminergic commitment for many weeks when cultured in 3% O 2 , whereas exposing these cells to 21% oxygen prohibited long-term expansion. Microarray data suggest that a variety of genes related to the cell cycle, cell maturation and apoptosis are differentially regulated in midbrain-derived precursors cultured in 3 versus 21% oxygen after 1-2 months. Taken together, we hypothesize that sustained high oxygen has deleterious effects on the self-renewal capacity of mesencephalic neural precursors, possibly accelerating maturation and senescence resulting in overall cell loss. Gene regulation governed by low oxygen tension may be relevant to the normal development and survival of midbrain neurons. Keywords: microarray, neural precursors, neurospheres, oxygen, proliferation, telomerase. Stem cells are undifferentiated cells that retain the ability to divide and proliferate throughout postnatal life to provide precursor cells that can differentiate into specialized cells. Neural stem cells can give rise to all the cells of the CNS including glial and neuronal cells (Gage 2003). As a result of their ability to differentiate following transplantation, these cells represent a potentially valuable therapeutic tool for the treatment of genetic, traumatic, inflammatory or degenerative neurological disorders (Studer et al. 1998;Storch and Schwarz 2002;Conti et al. 2003). To enable long-term expansion, all precursor cells must maintain the capacity to self-renew and a positive balance of proliferation versus differentiation or cell death. Therefore, it is crucial to understand the mechanisms governing cell division, differentiation and senescence (Sharpless and DePinho 2004).Mammals have evolved complex circulatory systems to ensure that every cell receives sufficient oxygen for normal metabolic processes. Lack of oxygen is defined as a reduction in oxygen supply to the tissues to below physiological levels. Hypoxia can develop as a result of ischaemia, representing a pathological component of stroke and heart attack. In addition to being a consequence of the growth of a malignant tumour and so a potential marker, hypoxia also acts to promote tumour development (Brizel et al. 1996;Brat et al. 2004). Address correspondence and reprint requests to Javorina Milosevic, Department of Neurology, Max-Bürger-Forschungszentrum, Johannisallee 30, 04103 Leipzig, Germany. E-mail: javorina.Milosevic@medizin.uni-leipzig.deAbbreviations used: ADA, adenosine deaminase; bFGF, basic fibroblast growth factor; BrdU, 5-bromo-2-deoxyuridine; DA, dopamine; DAPI, 6¢-diamidino-2-phenylindole; DMEM, Dulbecco's modified Eagle's medium; EGF...

Treatment with modafinil significantly improves fatigue and sleepiness and is well tolerated by patients with MS. Unlike the higher dose regimen required in narcolepsy, a low-dose regimen of modafinil is effective in MS.

Global gene expression profiling was performed using RNA from adult human hippocampus-derived neuroprogenitor cells (NPCs) and multipotent frontal cortical fetal NPCs compared with adult human mesenchymal stem cells (hMSCs) as a multipotent adult stem cell control, and adult human hippocampal tissue, to define a gene expression pattern that is specific for human NPCs. The results were compared with data from various databases. Hierarchical cluster analysis of all neuroectodermal cell/tissue types revealed a strong relationship of adult hippocampal NPCs with various white matter tissues, whereas fetal NPCs strongly correlate with fetal brain tissue. However, adult and fetal NPCs share the expression of a variety of genes known to be related to signal transduction, cell metabolism and neuroectodermal tissue. In contrast, adult NPCs and hMSCs overlap in the expression of genes mainly involved in extracellular matrix biology. We present for the first time a detailed transcriptome analysis of human adult NPCs suggesting a relationship between hippocampal NPCs and white matter-derived precursor cells. We further provide a framework for standardized comparative gene expression analysis of human brain-derived NPCs with other stem cell populations or differentiated tissues.