Bright light exposure reduces TH-positive dopamine neurons: implications of light pollution in Parkinson's disease epidemiology

Document Type

Article

Abstract

This study explores the effect of continuous exposure to bright light on neuromelanin formation and dopamine neuron survival in the substantia nigra. Twenty-one days after birth, Sprague-Dawley albino rats were divided into groups and raised under different conditions of light exposure. At the end of the irradiation period, rats were sacrificed and assayed for neuromelanin formation and number of tyrosine hydroxylase (TH)-positive neurons in the substantia nigra. The rats exposed to bright light for 20 days or 90 days showed a relatively greater number of neuromelanin-positive neurons. Surprisingly, TH-positive neurons decreased progressively in the substantia nigra reaching a significant 29% reduction after 90 days of continuous bright light exposure. This decrease was paralleled by a diminution of dopamine and its metabolite in the striatum. Remarkably, in preliminary analysis that accounted for population density, the age and race adjusted Parkinson's disease prevalence significantly correlated with average satellite-observed sky light pollution.

Medical Subject Headings

Animals; Dopaminergic Neurons (metabolism, radiation effects); Environmental Exposure; Humans; Light (adverse effects); Luminescence; Male; Melanins (metabolism); Neurotransmitter Agents (metabolism); Optic Nerve (metabolism); Parkinson Disease (epidemiology, etiology, metabolism); Prevalence; Rats; Substantia Nigra (metabolism); Tyrosine 3-Monooxygenase (metabolism); United States (epidemiology)

Publication Date

1-1-2013

Publication Title

Scientific reports

E-ISSN

2045-2322

Volume

3

First Page

1395

PubMed ID

23462874

Digital Object Identifier (DOI)

10.1038/srep01395

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