Light-at-Night (LAN) as a General Stressor

Abstract

The suppression of MLT by exposure to Light at Night (LAN) and its effects on daily rhythms are well documented in the literature. Throughout the years of research it has been noted that MLT treatment could not compensate for all the effects of LAN exposure and, therefore, we can conclude that other responses may result from the exposure to LAN. The idea that LAN is a general stressor was tested in the social vole Microtus socialis and an increase in adrenaline and cortisol production was detected. Recently it was also shown that LAN increases the expression of the gene hsp70 and the protein HSP70 in the brain and liver of golden spiny mice Acomys russatus, with the response levels in both tissues decreasing with the duration of acclimation. However, in the same animals, the response of the cardiocytes increased with the duration of acclimation thus indicating that different tissues respond to LAN in different ways. The fact that MLT treatment attenuates the response to LAN points to the fact that MLT may reduce negative impacts of LAN as a general stressor.

Stress is a non-specific body response to environmental changes that endangers life.

Selye (1950)