[show abstract][hide abstract] ABSTRACT: Abnormalities of striatal glutamate neurotransmission may play a role in the pathophysiology of Parkinson's disease and may respond to neurosurgical interventions, specifically stimulation or lesioning of the subthalamic nucleus (STN). The major glutamatergic afferent pathways to the striatum are from the cortex and thalamus, and are thus likely to be sources of striatal neuronally-released glutamate. Corticostriatal terminals can be distinguished within the striatum at the electron microscopic level as their synaptic vesicles contain the vesicular glutamate transporter, VGLUT1. The majority of terminals which are immunolabeled for glutamate but are not VGLUT1 positive are likely to be thalamostriatal afferents. We compared the effects of short term, high frequency, STN stimulation and lesioning in 6-hydroxydopamine (6OHDA)-lesioned rats upon striatal terminals immunolabeled for both presynaptic glutamate and VGLUT1. 6OHDA lesions resulted in a small but significant increase in the proportions of VGLUT1-labeled terminals making synapses on dendritic shafts rather than spines. STN stimulation for one hour, but not STN lesions, increased the proportion of synapses upon spines. The density of presynaptic glutamate immuno-gold labeling was unchanged in both VGLUT1-labeled and -unlabeled terminals in 6OHDA-lesioned rats compared to controls. Rats with 6OHDA lesions+STN stimulation showed a decrease in nerve terminal glutamate immuno-gold labeling in both VGLUT1-labeled and -unlabeled terminals. STN lesions resulted in a significant decrease in the density of presynaptic immuno-gold-labeled glutamate only in VGLUT1-labeled terminals. STN interventions may achieve at least part of their therapeutic effect in PD by normalizing the location of corticostriatal glutamatergic terminals and by altering striatal glutamatergic neurotransmission.
PLoS ONE 01/2012; 7(3):e32919. · 3.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: The purpose of this chapter is to first describe common clinical and laboratory tests and measures used to capture alterations
in motor control in individuals with Parkinson’s disease (PD) and secondly, to detail both morphological and motor tests that
are used in two rodent models of PD. For the description in humans, it is organized within the body structure and function and activity categories of the International Classification of Functioning, Disability, and Health (ICF). Specific tests discussed include
the retropulsion test, turning test, Unified Parkinson’s Disease Rating Scale, Timed Up-and-Go, Berg Balance Scale, electromyography,
quantitative digitography, motion analysis, and force plate perturbation. Testing procedure, set-up, and interpretation are
described and examples of application in the PD population are provided. We hope that clinicians and researchers develop a
beginning understanding of the different methods available for examining alterations in motor control in individuals with
PD. Using the rat model of PD, we first describe in detail a new ultrastructural processing method that is used not only to
process tissue but also to localize specific proteins that can then be used to correlate synaptic changes with motor alterations
that are observed following depletion of dopamine. Finally, using a mouse model of PD, we describe three locomotor tests that
can be quantified and correlated with the loss of dopamine-labeled neurons in the substantia nigra.
Key words:Parkinson’s disease-MPTP-motor behavior-electron microscopy
[show abstract][hide abstract] ABSTRACT: The SLC30A8 gene codes for a pancreatic beta-cell-expressed zinc transporter, ZnT8. A polymorphism in the SLC30A8 gene is associated with susceptibility to type 2 diabetes, although the molecular mechanism through which this phenotype is manifest is incompletely understood. Such polymorphisms may exert their effect via impacting expression level of the gene product. We used an shRNA-mediated approach to reproducibly downregulate ZnT8 mRNA expression by >90% in the INS-1 pancreatic beta cell line. The ZnT8-downregulated cells exhibited diminished uptake of exogenous zinc, as determined using the zinc-sensitive reporter dye, zinquin. ZnT8-downregulated cells showed reduced insulin content and decreased insulin secretion (expressed as percent of total insulin content) in response to hyperglycemic stimulus, as determined by insulin immunoassay. ZnT8-depleted cells also showed fewer dense-core vesicles via electron microscopy. These data indicate that reduced ZnT8 expression in cultured pancreatic beta cells gives rise to a reduced insulin response to hyperglycemia. In addition, although we provide no direct evidence, these data suggest that an SLC30A8 expression-level polymorphism could affect insulin secretion and the glycemic response in vivo.
PLoS ONE 01/2009; 4(5):e5679. · 3.73 Impact Factor