Figure 2.

Schematic changes found in mice and rats chronically exposed to different lighting protocols which might induce circadian and metabolic alterations. Actograms double plotted at modulo 24 h show alterations in the behavioral activity rhythm. Compared to standard light:dark (LD) conditions: (1) LD_LAN (light at night) promotes a dispersed rhythm increasing both general and feeding activity bouts at the light phase, together with reduced suprachiasmatic nucleus (SCN) and liver clock-genes amplitude; (2) LL generates behavioral arrhythmicity with loss of the feeding/fasting rhythm, also with dampened amplitude of SCN and liver clock-genes rhythms; (3) forced desynchrony protocols (i.e., chronic jetlag—CJL—and T cycles) generate two activity components at the behavioral and SCN clock-gene (regional) levels, with disrupted daily feeding/fasting rhythms, and with liver clock genes out of phase. Dampened melatonin rhythms occur both under LL and LD_LAN, while this rhythm is out of phase under forced desynchronization. All lighting protocols promote a decrease in the insulin sensitivity rhythm, and an increased weight gain respect to LD.