Exposure to 2500 lux increases serum melatonin in venezuelan equine encephalomyelitis

When mice infected with the Venezuelan equine encephalomyelitis (VEE) virus were exposed to 2500 lux with a 12 h light: 12 h dark photoperiod, the ser um levels of melatonin (MLT) remained constantly elevated. In mice exposed to 400 lux low levels of serum MLT were detected during the day and high le vels during the night. An increase in the survival rate of the infected mic e from 6 to 13 days after virus inoculation was also observed. The signific ant increment in the concentration of serum MLT produced by the high intens ity light could be responsible for the longer survival rate of mice infecte d with the VEE virus.