Brain-derived neurotrophic factor (BDNF) modulates the synaptic transmission of several monoaminergic neuronal systems, including forebrain dopamine-containing neurons. Recent evidence shows a strong correlation between neuropsychiatric disorders and BDNF hypofunction. The aim of the present study was to characterize the effect of low endogenous levels of BDNF on dopamine system function in the caudate-putamen using heterozygous BDNF (BDNF+/−) mice. Apparent extracellular dopamine levels in the caudate-putamen, determined by quantitative microdialysis, were significantly elevated in BDNF+/− mice compared to wildtype controls (12 vs. 5 nM, respectively). BDNF+/− mice also had a potentiated increase in dopamine levels following potassium (120 mM)-stimulation (10-fold) relative to wildtype controls (6-fold). Slice fast-scan cyclic voltammetry revealed that BDNF+/− mice had reductions in both electrically-evoked dopamine release and dopamine uptake rates in the caudate-putamen. Superfusion of BDNF led to partial recovery of the electrically-stimulated dopamine release response in BDNF+/− mice. Conversely, tissue accumulation of L-3,4-dihydroxyphenylalanine, extracellular levels of dopamine metabolites, and spontaneous locomotor activity were unaltered. Together, this study indicates that endogenous BDNF influences dopamine system homeostasis by regulating the release and uptake dynamics of presynaptic dopamine transmission.

The voltammetry of solution-dispersed magnetite iron oxide Fe3O4 nanoparticles is described. Their currents are controlled by nanoparticle transport rates, as shown with potential step chronoamperometry and rotated disk voltammetry. In pH 2 citrate buffer with added NaClO4 electrolyte, solution cyclic voltammetry of these nanoparticles (average diameter 4.4 ± 0.9 nm, each containing ca. 30 Fe sites) displays an electrochemically irreversible oxidation with E(PEAK) at ca. +0.52 V and an irreversible reduction with E(PEAK) at ca. +0.2 V vs Ag/AgCl reference electrode. These processes are presumed to correspond to the formal potentials for one-electron oxidation of Fe(II) and reduction of Fe(III) at their different sites in the magnetite nanoparticle structure. The heterogeneous electrode reaction rates of the nanoparticles are very slow, in the 10(-5) cm/s range. The nanoparticles are additionally characterized by a variety of tools, e.g., TEM, UV/vis, and XPS spectroscopies.

Indium-tin oxide (ITO) nanoparticles, 6.1 ± 0.8 nm in diameter, were synthesized using a hot injection method. After reaction with 3-aminopropyldimethylethoxysilane to replace the initial oleylamine and oleic acid capping ligands, the aminated nanoparticles were rendered electroactive by functionalization with ferrocenoyl chloride. The nanoparticle color changed from blue-green to light brown, and the nanoparticles became more soluble in polar solvents, notably acetonitrile. The nanoparticle diffusion coefficient (D = 1.0 × 10(-6) cm(2)/s) and effective ferrocene concentration (C = 0.60 mM) in acetonitrile solutions were determined using ratios of DC and D(1/2)C data measured by microdisk voltammetry and chronoamperometry. The D result compares favorably to an Einstein-Stokes estimate (2.1 × 10(-6) cm(2)/s), assuming an 8 nm hydrodynamic diameter in acetonitrile (6 nm for the ITO core plus 2 nm for the ligand shell). The ferrocene concentration result is lower than anticipated (ca. 1.60 mM) based on a potentiometric titration of the ferrocene sites with Cu(II) in acetonitrile. Cyclic voltammetric data indicate tendency of the ferrocenated nanoparticles to adsorb on the Pt working electrode.

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