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Extracellular ascorbate modulates glutamate dynamics: role of behavioral activation.

Sandstrom MI, Rebec GV - BMC Neurosci (2007)

Bottom Line: A physiological increase in extracellular ascorbate (AA), an antioxidant vitamin found throughout the striatum, elevates extracellular glutamate (GLU).Interestingly, when ambient light returned to the lights-off group, 1000 microM prolonged the GLU increase relative to the 250 microM group.Our results not only support evidence that elevated striatal AA increases extracellular GLU but also indicate that this effect depends on behavioral state and the corresponding level of endogenous GLU release.

View Article: PubMed Central - HTML - PubMed

Affiliation: Central Michigan University, Psychology Department, Mount Pleasant, MI, USA. sands1m@cmich.edu <sands1m@cmich.edu>

ABSTRACT

Background: A physiological increase in extracellular ascorbate (AA), an antioxidant vitamin found throughout the striatum, elevates extracellular glutamate (GLU). To determine the role of behavioral arousal in this interaction, microdialysis was used to measure striatal GLU efflux in rats tested in either a lights-off or lights-on condition while reverse dialysis either maintained the concentration of AA at 250 microM or increased it to 1000 microM to approximate endogenous changes.

Results: When lights were off, both locomotion and GLU increased regardless of AA dose. In contrast, animals in the lights-on condition were behaviorally inactive, and infusion of 1000, but not 250, microM AA significantly increased extracellular GLU. Interestingly, when ambient light returned to the lights-off group, 1000 microM prolonged the GLU increase relative to the 250 microM group.

Conclusion: Our results not only support evidence that elevated striatal AA increases extracellular GLU but also indicate that this effect depends on behavioral state and the corresponding level of endogenous GLU release.

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Representative microdialysis probe placement shown in a 40 μm coronal section. Wider cortex damage represents the intracerebral guide cannula termination, while the gliosis seen ventrally shows the typical terminal end of the 4.0 mm semipermeable microdialysis probe tip.
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Figure 3: Representative microdialysis probe placement shown in a 40 μm coronal section. Wider cortex damage represents the intracerebral guide cannula termination, while the gliosis seen ventrally shows the typical terminal end of the 4.0 mm semipermeable microdialysis probe tip.

Mentions: After completion of the second dialysis session, each rat was transcardially perfused with formosaline, and brain slices were mounted on microscope slides for verification of probe placement. Only data from subjects with appropriately placed probe-related gliosis in anterior striatum were analyzed further. A representative section is shown in Fig. 3.


Extracellular ascorbate modulates glutamate dynamics: role of behavioral activation.

Sandstrom MI, Rebec GV - BMC Neurosci (2007)

Representative microdialysis probe placement shown in a 40 μm coronal section. Wider cortex damage represents the intracerebral guide cannula termination, while the gliosis seen ventrally shows the typical terminal end of the 4.0 mm semipermeable microdialysis probe tip.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1884166&req=5

Figure 3: Representative microdialysis probe placement shown in a 40 μm coronal section. Wider cortex damage represents the intracerebral guide cannula termination, while the gliosis seen ventrally shows the typical terminal end of the 4.0 mm semipermeable microdialysis probe tip.
Mentions: After completion of the second dialysis session, each rat was transcardially perfused with formosaline, and brain slices were mounted on microscope slides for verification of probe placement. Only data from subjects with appropriately placed probe-related gliosis in anterior striatum were analyzed further. A representative section is shown in Fig. 3.

Bottom Line: A physiological increase in extracellular ascorbate (AA), an antioxidant vitamin found throughout the striatum, elevates extracellular glutamate (GLU).Interestingly, when ambient light returned to the lights-off group, 1000 microM prolonged the GLU increase relative to the 250 microM group.Our results not only support evidence that elevated striatal AA increases extracellular GLU but also indicate that this effect depends on behavioral state and the corresponding level of endogenous GLU release.

View Article: PubMed Central - HTML - PubMed

Affiliation: Central Michigan University, Psychology Department, Mount Pleasant, MI, USA. sands1m@cmich.edu <sands1m@cmich.edu>

ABSTRACT

Background: A physiological increase in extracellular ascorbate (AA), an antioxidant vitamin found throughout the striatum, elevates extracellular glutamate (GLU). To determine the role of behavioral arousal in this interaction, microdialysis was used to measure striatal GLU efflux in rats tested in either a lights-off or lights-on condition while reverse dialysis either maintained the concentration of AA at 250 microM or increased it to 1000 microM to approximate endogenous changes.

Results: When lights were off, both locomotion and GLU increased regardless of AA dose. In contrast, animals in the lights-on condition were behaviorally inactive, and infusion of 1000, but not 250, microM AA significantly increased extracellular GLU. Interestingly, when ambient light returned to the lights-off group, 1000 microM prolonged the GLU increase relative to the 250 microM group.

Conclusion: Our results not only support evidence that elevated striatal AA increases extracellular GLU but also indicate that this effect depends on behavioral state and the corresponding level of endogenous GLU release.

Show MeSH
Related in: MedlinePlus