Fluoxetine normalizes disrupted light-induced entrainment, fragmented ultradian rhythms and altered hippocampal clock gene expression in an animal model of high trait anxiety- and depression-related behavior

Figures & data

Figure 1. Experimental procedure for the assessment of the effects of chronic fluoxetine treatment on behavioral and molecular parameters of the circadian clock in HAB and NAB mice. Depicted is the time course (in days) of drug administration (dashed line) and respective light regimes light/dark (LD): 12h light and 12h dark phase, white boxes; dark/dark (DD): 24 h constant darkness, black boxes) for the experimental evaluation of the effects of chronic fluoxetine treatment on circadian wheel-running activity and hippocampal clock gene expression in female mice selectively bred for high (HAB) and normal (NAB) anxiety-related and depression-like behavior.

Table 1. Unaltered mRNA expression of clock genes and clock-controlled genes in the hippocampus of NAB versus HAB mice under chronic fluoxetine treatment.

mRNA	NAB	HAB	p value
Clock	1.000 ± 0.024	0.979 ± 0.061	0.7615
Bmal1	1.000 ± 0.037	0.919 ± 0.080	0.3758
Per1	1.000 ± 0.119	1.070 ± 0.064	0.6155
Cry1	1.000 ± 0.054	1.156 ± 0.104	0.2054
Cry2	1.000 ± 0.015	1.039 ± 0.062	0.5545
Rorα	1.000 ± 0.110	1.285 ± 0.218	0.2847
Rorβ	1.000 ± 0.026	1.028 ± 0.114	0.8153
Rorγ	1.000 ± 0.815	1.048 ± 0.148	0.8378
Rev-erbα	1.000 ± 0.056	0.991 ± 0.110	0.9429
Rev-erbβ	1.000 ± 0.094	1.021 ± 0.086	0.8739
Npas2	1.000 ± 0.067	0.991 ± 0.146	0.9572

Mean HAB fold-change values (n = 7–8 per group) are normalized to NAB means for each gene analyzed and are displayed as mean ± SEM. p values derived from statistical comparisons using two-tailed Student-t-tests are provided.

Figure 2. Circadian period (tau) and wheel-running activity rhythms in fluoxetine-treated HAB and NAB mice. During chronic fluoxetine treatment HAB mice showed a longer circadian period (tau) than NAB mice both under (a) light-entrained (LD) and under (b) free-running (DD) conditions as compared with no treatment (previously reported in (23) and reprinted here in inserts (with permission from Annals of Medicine). No differences in the total amount of wheel-running activity per day between HAB and NAB mice was detected, nor during either their active (alpha) or inactive (rho) under (c) light-entrained and (d) free-running conditions (n= 8–16 per group). **p < 0.01, n.s. (not significant), p > 0.05. All data are displayed as mean ± SEM.

Figure 3. Circadian wheel-running activity bouts in HAB and NAB mice under chronic fluoxetine treatment. Sample actograms illustrating circadian wheel-running activity in chronically-fluoxetine treated (a) NAB and (b) HAB mice. NAB and HAB mice show comparable numbers of daily wheel-running activity bouts under (c) light-entrained (LD) and (d) free-running conditions (DD) (n= 8–16 per group). Inserts (reprinted with permission from Annals of Medicine) represent previously obtained results in untreated HAB and NAB mice (23). n.s. (not significant) p > 0.05. All data are displayed as mean ± SEM.

Figure 4.Phase shift response and relative hippocampal clock gene expression in HAB and NAB mice chronically treated with fluoxetine. (a) The phase shift response upon exposure to a brief light pulse at CT14 is comparable in HAB and NAB mice (n= 8–16 per group). Inserts (reprinted with permission from Annals of Medicine) represent previously obtained results in untreated HAB and NAB mice (23). (b) Per2 and (c) Per3 mRNA expression and (d) Per3 protein expression is significantly higher in hippocampal tissue of fluoxetine-treated HAB as compared to NAB mice (n = 7–8 per group). *p < 0.05, ***p < 0.001. All data are data displayed as mean ± SEM.

Griesauer I, Diao W, Ronovsky M, Elbau I, Sartori S, Singewald N, et al. Circadian abnormalities in a mouse model of high trait anxiety and depression. Ann Med. 2014;46:148–54.

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