NathanK
Member
Bright light exposure reduces TH-positive dopamine neurons: implications of light pollution in Parkinson's disease epidemiology
http://www.ncbi.nlm.nih.gov/pubmed/23462874 Full text: http://digitalcommons.wustl.edu/open_access_pubs/1333/
The study used bright (fluorescent) light on surgically blinded mice and found it oxidized dopamine at a much faster rate ultimately impairing dopaminergic neurons in the substantia nigra. The wavelength penetrated the brain where dopamine interacted with iron to auto-oxidize (essentially giving them Parkinsons). In contrast, near IR is neuroprotective of those neurons.
...two broad bands of dopamine absorbance appear, with maxima at 437 and 740 nm. Although light with longer wavelengths penetrates into the brain more effectively8, shorter wavelength light can also penetrate into deep brain structures and regulate, for example, the seasonal cycle of reproduction in birds9. For instance, opsin 5, a non-retinal and non-pineal deep-brain opsin photoreceptor in the hypothalamus of quail, has a peak of excitation at 419 nm10. Penetration of light into the brain has also been demonstrated in larger animals, including sheep and dog11.
...Unexpectedly, in our study we also observed a significant decrease in TH-positive neurons in the substantia nigra after continuous bright light exposure that was paralleled by a significant reduction in dopamine and DOPAC in the striatum. As an internal control, in the same animals, 5-hydroxytryptamine and 5-HIAA did not diminish, indicating that the effect of light was specific to the dopaminergic neurons.
...The fluorescent lighting spectrum of the lamp we used to irradiate the animals shows peaks in the same range of the absorbance of dopamine in complex with Fe3+, for example, a peak at 436.6 nm and several minor peaks around 710 nm. At the end of the light exposure period in a rat of ~400 g, the percentage of energy that crossed the scalp and the skull was about ~0.1% for the peak at 436.6 nm and ~15% for the minor peaks around 710 nm. Together, these data would suggest that external light passes through the head of the animal, reaches the substantia nigra, hits dopamine in complex with Fe3+, and triggers its auto-oxidation
...near-infrared light treatment neuroprotects dopaminergic cells in the substantia nigra pars compacta and the zona incerta of the hypothalamus from degeneration in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice.
...continuous exposure to light increases dopaminergic function as a consequence of light-induced stress and increase in corticosterone levels. Beside corticosterone, other hormones could be altered by continuous light exposure. For instance, melatonin secretion is suppressed by light and alteration of its level could influence dopamine content in the striatum25
...One would suspect that the amount of light that reaches the substantia nigra in the human brain—for the size of the head, the thickness of the skull and the deep brain localization of the substantia nigra—will be negligible. However, scientific data refutes that assumption...This observation suggests that a tiny amount of light can reach deep brain structures in human beings and this amount is proportional to the length of exposure and the brightness of the light source
...the spectral characteristics of artificial light, especially fluorescent light, are completely different from sunlight, as the sunlight spectrum is continuous while fluorescent light spectrum is discontinuous and shows several peaks. Light frequencies of the sunlight spectrum could protect rather than damage the dopamine neurons, as we have mentioned above for near-infrared ligh
I posted this in Valtsu's LLLT and Photomodulation FB group the other day and figured I'd share here. The purpose of the study was to see how light pollution might be affected us, but I think it raises some good questions since most of us spend our time indoors.
-While most of us will not become afflicted with Parkinson's in our lives, how could a lifetime of bright light exposure affect us? The study shows the mice oxidized dopamine at a much higher rate due to bright light stimulation and therefore "burnt out" faster. Cumulative bright light damage could mean less dopamine and overall happiness over time. IOW, at the age of 40 we would have less dopamine than if were living 50 years ago. Most of us are living in the first generation of CFL and fluorescent light usage with no proof of their safety long term.
-Using blue blocker glasses, as many do, likely does not prevent all stimulatory wavelengths as we may have assumed. These mice were surgically blinded.
-This study reminded me of how researchers first discovered the perfect drug to deplete dopamine in studies. In Southern California years ago some young patients showed up in the emergency room with full blown Parkinson's. This was surprising because Parkinson's is a progressive disease that usually manifests in your 60's. These kids had found a way to manufacture "China White" heroin and subsequently destroyed their substantia negra. Amphetamines like ephedrine and cocaine can similarly "burn out" dopamine "receptors" with continuous use. Can these bright lights do so as well over time?
-This is yet another reason to keep iron stores low, or at least in check, as less iron means less dopamine to oxidize. People with Parkinson's are known to have high levels of iron in the brain.
http://www.ncbi.nlm.nih.gov/pubmed/23462874 Full text: http://digitalcommons.wustl.edu/open_access_pubs/1333/
The study used bright (fluorescent) light on surgically blinded mice and found it oxidized dopamine at a much faster rate ultimately impairing dopaminergic neurons in the substantia nigra. The wavelength penetrated the brain where dopamine interacted with iron to auto-oxidize (essentially giving them Parkinsons). In contrast, near IR is neuroprotective of those neurons.
...two broad bands of dopamine absorbance appear, with maxima at 437 and 740 nm. Although light with longer wavelengths penetrates into the brain more effectively8, shorter wavelength light can also penetrate into deep brain structures and regulate, for example, the seasonal cycle of reproduction in birds9. For instance, opsin 5, a non-retinal and non-pineal deep-brain opsin photoreceptor in the hypothalamus of quail, has a peak of excitation at 419 nm10. Penetration of light into the brain has also been demonstrated in larger animals, including sheep and dog11.
...Unexpectedly, in our study we also observed a significant decrease in TH-positive neurons in the substantia nigra after continuous bright light exposure that was paralleled by a significant reduction in dopamine and DOPAC in the striatum. As an internal control, in the same animals, 5-hydroxytryptamine and 5-HIAA did not diminish, indicating that the effect of light was specific to the dopaminergic neurons.
...The fluorescent lighting spectrum of the lamp we used to irradiate the animals shows peaks in the same range of the absorbance of dopamine in complex with Fe3+, for example, a peak at 436.6 nm and several minor peaks around 710 nm. At the end of the light exposure period in a rat of ~400 g, the percentage of energy that crossed the scalp and the skull was about ~0.1% for the peak at 436.6 nm and ~15% for the minor peaks around 710 nm. Together, these data would suggest that external light passes through the head of the animal, reaches the substantia nigra, hits dopamine in complex with Fe3+, and triggers its auto-oxidation
...near-infrared light treatment neuroprotects dopaminergic cells in the substantia nigra pars compacta and the zona incerta of the hypothalamus from degeneration in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice.
...continuous exposure to light increases dopaminergic function as a consequence of light-induced stress and increase in corticosterone levels. Beside corticosterone, other hormones could be altered by continuous light exposure. For instance, melatonin secretion is suppressed by light and alteration of its level could influence dopamine content in the striatum25
...One would suspect that the amount of light that reaches the substantia nigra in the human brain—for the size of the head, the thickness of the skull and the deep brain localization of the substantia nigra—will be negligible. However, scientific data refutes that assumption...This observation suggests that a tiny amount of light can reach deep brain structures in human beings and this amount is proportional to the length of exposure and the brightness of the light source
...the spectral characteristics of artificial light, especially fluorescent light, are completely different from sunlight, as the sunlight spectrum is continuous while fluorescent light spectrum is discontinuous and shows several peaks. Light frequencies of the sunlight spectrum could protect rather than damage the dopamine neurons, as we have mentioned above for near-infrared ligh
I posted this in Valtsu's LLLT and Photomodulation FB group the other day and figured I'd share here. The purpose of the study was to see how light pollution might be affected us, but I think it raises some good questions since most of us spend our time indoors.
-While most of us will not become afflicted with Parkinson's in our lives, how could a lifetime of bright light exposure affect us? The study shows the mice oxidized dopamine at a much higher rate due to bright light stimulation and therefore "burnt out" faster. Cumulative bright light damage could mean less dopamine and overall happiness over time. IOW, at the age of 40 we would have less dopamine than if were living 50 years ago. Most of us are living in the first generation of CFL and fluorescent light usage with no proof of their safety long term.
-Using blue blocker glasses, as many do, likely does not prevent all stimulatory wavelengths as we may have assumed. These mice were surgically blinded.
-This study reminded me of how researchers first discovered the perfect drug to deplete dopamine in studies. In Southern California years ago some young patients showed up in the emergency room with full blown Parkinson's. This was surprising because Parkinson's is a progressive disease that usually manifests in your 60's. These kids had found a way to manufacture "China White" heroin and subsequently destroyed their substantia negra. Amphetamines like ephedrine and cocaine can similarly "burn out" dopamine "receptors" with continuous use. Can these bright lights do so as well over time?
-This is yet another reason to keep iron stores low, or at least in check, as less iron means less dopamine to oxidize. People with Parkinson's are known to have high levels of iron in the brain.