Fig. 5. Effects of 8-Br-cGMP on levels of locomotor activity, age at onset of circadian locomotor rhythms, and tau (the period of rhythmicity) under (A) 12 h:12 h light:dark (L:D) and (B) 24 h dark (D:D) regimes. Activity levels were analyzed only under L:D conditions because light entrains activity. There were no significant differences between the different groups in all experiments (activity, tau, ANOVA; % rhythmicity, P>0.05; ² tests).