Fig. 1

DD altered activity patterns, body and reproductive organs weight. Rats were raised under the controlled light regime of 14 h light–10 h dark (LD) or were exposed to constant dark conditions (DD) until 35, 42, and 90 pnd. From pnd 60 to 90, the rats’ voluntary activity was monitored. The DD changed the rhythmic pattern of rats’ voluntary activity (A, the 30-day average of activity monitoring is displayed on a 24-hour axis; LD – upper panel; DD – lower panel). DD decreased daily activity (B, data presented as Whisker box). Rats were monitored for body mass (C) and weight of testes (D), seminal vesicles (E), and prostates (F, G). Data bars represent group means ± SEM values; dots illustrate individual values (n = 4–6). *Statistical significance at level p < 0.05 compared to the corresponding LD group.