Whitney Badal, Brigham Young University
Life Sciences
Light therapy has been utilized to treat alcoholism and opiate-dependent rats as well as ameliorating symptoms of Parkinson’s disease. As both addiction and Parkinson’s Disease (PD) are often associated with decreased dopamine transmission in the striatum, it is likely that light therapy is able to increase dopamine release. A similar technique called near-infrared light treatment has also been shown to be effective in mice in restoring the function of dopamine cells in the substantia nigra pars compacta (an area associated with PD). A possible explanation for this is that light catalyzes the formation of neuromelanin. It is likely that neuromelanin is a neuroprotective cellular agent that is able to reduce damage caused by reactive oxygen species. Using UV-IR spectrophotometry, we show that in the presence of photostimulation, dopamine (0.3-30 uM) oxidizes and polymerizes into neuromelanin. Since hydrogen peroxide catalyzes this formation of neuromelanin, it is likely that this is a radical-polymerization reaction, suggesting that neuromelanin may be a radical scavenger. Additionally, the presence of the selective iron chelator desferrioxamine, the calcium chelator EGTA, or lack of calcium in the artificial cerebral spinal fluid markedly reduces the formation of neuromelanin. Using fast scan cyclic voltammetry in mouse horizontal and/or coronal brain slices, dopamine release in the nucleus accumbens core was enhanced by light exposure, in particular UV and short-wavelength visible light. These findings indicate that both iron and calcium are necessary for melanization in neural tissues and that light-induced melanization enhances dopamine release, suggesting a physiological role for melanization in synaptic transmission.