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l-DOPA is still the drug of choice to treat Parkinson’s disease although adverse side effects appear after several years of treatment. These are thought to be the consequence of plastic re-arrangements of the nigrostriatal connections, such as sprouting of the dopaminergic terminals or post-synaptic changes. Pleiotrophin, a trophic factor that we have shown to be up-regulated in the striatum of parkinsonian rats after long-terml-DOPA treatment may play a role in these plastic changes. To determine whether one of the three known pleiotrophin receptors [ N-syndecan, receptor protein tyrosine phosphatase type zeta beta (RPTP-ζ/β) and anaplastic lymphoma kinase] might be implicated in these putative plastic effects, we quantified their expression levels by real-time RT-PCR in the striatum and mesencephalon of rats with partial lesions of the nigrostriatal pathway undergoingl-DOPA treatment. Both pleiotrophin and RPTP-ζ/β expression was up-regulated in the striatum but not in the mesencephalon of lesioned rats and RPTP-ζ/β expression was even further increased byl-DOPA. The levels of the RPTP-ζ/β protein were also increased in the striatum ofl-DOPA-treated lesioned rats. Immunofluorescence labeling showed the protein to be constitutively expressed in striatal medium spiny neurons, which are innervated by both the corticostriatal glutamatergic and nigrostriatal dopaminergic systems. RPTP-ζ/β might therefore be implicated in the plastic changes triggered byl-DOPA treatment and might merit further study as a potential candidate for Parkinon’s disease therapy. [ABSTRACT FROM AUTHOR]

Mutations in two kinases, PTEN induced kinase 1 (PINK1) and leucine-rich repeat kinase 2 (LRRK2), have been shown to segregate with familial forms of Parkinson's disease. Although these two genes are expected to be involved in molecular mechanisms relevant to Parkinson's disease, their precise anatomical localization in mammalian brain is unknown. We have mapped the expression of PINK1 and LRRK2 mRNA in the rat and mouse brain via in situ hybridization histochemistry using riboprobes. We found that both genes are broadly expressed throughout the brain with similar neuroanatomical distribution in mouse compared to rat. PINK1 mRNA abundance was rather uniform throughout the different brain regions with expression in cortex, striatum, thalamus, brainstem and cerebellum. LRRK2, on the other hand, showed strong regional differences in expression levels with highest levels seen in the striatum, cortex and hippocampus. Weak LRRK2 expression was seen in the hypothalamus, olfactory bulb and substantia nigra. We confirmed these distributions for both genes using quantitative RT-PCR and for LRRK2 by western immunoblot. As their broad expression patterns contrast with localized neuropathology in Parkinson's disease, the pathogenicity of clinical mutant forms of PINK1 and LRRK2 may be mediated by nigrostriatal-specific mechanisms. [ABSTRACT FROM AUTHOR]

Abstract AMPA receptor-mediated neurotoxicity is currently the most plausible hypothesis for the etiology of amyotrophic lateral sclerosis (ALS). The mechanism initiating this type of neuronal death is believed to be exaggerated Ca[sup 2+]-influx through AMPA receptors, which is critically determined by the presence or absence of the glutamate receptor subunit 2 (GluR2) in the assembly. We have provided the first quantitative measurements of the expression profile of AMPA receptor subunits mRNAs in human single neurons by means of quantitative RT–PCR with a laser microdissector. Among the AMPA subunits, GluR2 shared the vast majority throughout the neuronal subsets and tissues examined. Furthermore, both the expression level and the proportion of GluR2 mRNA in motoneurons were the lowest among all neuronal subsets examined, whereas those in motoneurons of ALS did not differ from the control group, implying that selective reduction of the GluR2 subunit cannot be a mechanism of AMPA receptor-mediated neurotoxicity in ALS. However, the low relative abundance of GluR2 might provide spinal motoneurons with conditions that are easily affected by changes of AMPA receptor properties including deficient GluR2 mRNA editing in ALS. [ABSTRACT FROM AUTHOR]

In this study we have used mature, primary cultured mouse cerebellar granule cells (CGCs) to initiate our studies on the mechanisms governing neuronal trafficking of GABA[sub A] receptors (GABARs). Initially the steady-state distribution of GABAR α1, α6, β2 and β3 subunits between the cell surface and cell interior was quantified. Cell surface proteins were modified with a membrane-impermeable cross-linking agent, bis(sulfosuccinimidyl)suberate (BS[sup 3]) or the proteolytic enzyme, chymotrypsin. The proportion of unmodified (intracellular) and modified (cell surface) subunits was quantified by immunoblotting. We found that 51% of α6, 74% of α1, and 83% of β2/3 were expressed at the cell surface, thus identifying a sizeable intracellular pool of α6 in contrast to the low levels of intracellular α1 and β2/3. Chronic activation of protein kinase A (PKA) in CGCs in vitro, post-transcriptionally up-regulated expression of α1, β2 and β3 but not α6. This was paralleled by an increase in the BZ-S subtype of [[sup 3]H]Ro15–4513 binding sites. GABAR α1 was increased at the cell surface and in the cell interior, β2 was increased almost exclusively at the cell surface whilst β3 was increased almost exclusively in the cell interior. The intracellular pool of α6 was not affected. Thus, GABAR subunits are subject to differentially regulated trafficking, affording yet greater scope for GABAR diversity and plasticity. [ABSTRACT FROM AUTHOR]

The modulatory effects of Zn[sup 2+] and other divalent cations on the ATP-induced responses of preganglionic neurons acutely dissociated from the rat dorsal motor nucleus of the vagus (DMV) were examined using a nystatin-perforated patch technique under voltage-clamp. DMV neurons were identified by back-filling of DiI placed on the vagal bundle at the neck. Zn[sup 2+] exerts a concentration-dependent effect on P2X receptor-mediated current (I[sub ATP]): a potentiation by low concentrations of Zn[sup 2+] (≤ 50 µm) and an inhibition by high concentrations (> 50 µm). Inhibition of the ATP response was associated with a prolongation of the rising phase of I[sub ATP]. Cu[sup 2+] mimicked Zn[sup 2+] regarding the biphasic modulation of I[sub ATP]. On the other hand, Ni[sup 2+] potentiated, but failed to inhibit, the ATP response even at a concentration of 3 mm. Quantitative RT-PCR revealed the similarity of P2X[sub 2] mRNA expression between the DMV and superior cervical ganglion (SCG) but not in the dorsal root ganglion (DRG) and hypoglossal nucleus (XII). The results from the electrophysiological and molecular approaches suggest that functional P2X receptors expressed in DMV neurons are characterized mainly by the P2X[sub 2] and P2X[sub 2/6] subtype. DMV neurons possess similar P2X receptor characteristics to SCG neurons. [ABSTRACT FROM AUTHOR]