Chronic creatine supplementation alters depression-like behavior in rodents in a sex-dependent manner

Abstract

Impairments in bioenergetic function, cellular resiliency, and structural plasticity are associated with the pathogenesis of mood disorders. Preliminary evidence suggests that creatine, an ergogenic compound known to promote cell survival and influence the production and usage of energy in the brain, can improve mood in treatment-resistant patients. This study examined the effects of chronic creatine supplementation using the forced swim test (FST), an animal model selectively sensitive to antidepressants with clinical efficacy in human beings. Thirty male (experiment 1) and 36 female (experiment 2) Sprague-Dawley rats were maintained on either chow alone or chow blended with either 2% w/w creatine monohydrate or 4% w/w creatine monohydrate for 5 weeks before the FST. Open field exploration and wire suspension tests were used to rule out general psychostimulant effects. Male rats maintained on 4% creatine displayed increased immobility in the FST as compared with controls with no differences by diet in the open field test, whereas female rats maintained on 4% creatine displayed decreased immobility in the FST and less anxiety in the open field test compared with controls. Open field and wire suspension tests confirmed that creatine supplementation did not produce differences in physical ability or motor function. The present findings suggest that creatine supplementation alters depression-like behavior in the FST in a sex-dependent manner in rodents, with female rats displaying an antidepressant-like response. Although the mechanisms of action are unclear, sex differences in creatine metabolism and the hormonal milieu are likely involved.

Figure 1

Mean (±SEM) body weight, caloric intake, and water consumption of males did not vary as a function of creatine supplementation over 6 weeks (a–c). Separate one-way ANOVAs for weekly averages of daily water consumption indicate that rats given +4% creatine drank more water during week 1 (^**p<0.001 vs +0%, ^**p<0.008 vs +2%) and week 2 (^**p<0.007 vs +0%, ^*p<0.041 vs +2%), but this effect was no longer significant by the third week. There were no significant differences for the remainder of the study or during behavioral testing days.

Figure 2

Mean (±SEM) latency to immobility (a), immobility counts (b, c), swim counts (b, c), and climbing counts (b, c) of males as a function of creatine supplementation. Note that significance values displayed on graphs are derived from separate one-way ANOVAs for each FST trial compared with +0% controls. Repeated measures analyses indicate that (a, top panel) +4% creatine group more rapidly displayed immobility across trials (^**p<0.001, +4% vs +0% ^**p<0.001, +4% vs +2%). (b, c) Complementary pattern of results as measured by total immobility (*p=0.011; +4 vs +0% ^*p=0.027, +4 vs +2% creatine), swimming (^**p<0.001, +4 vs +0% ^**p<0.001, +4 vs +2%), and climbing (p>0.05, n.s.). Data are presented as latencies to become immobile in seconds (a), or total counts of immobility, swimming, or climbing (b, c).

Figure 3

Mean (±SEM) wire suspension (a) and open field (b, c) performance of males as a function of creatine supplementation. Locomotion, anxiety-like behavior, and muscle strength did not vary by diet. Data for time in center and latency to enter center are represented by a subset of the total number of rats (+0%: n=9; +2%: n=8; +4% n=9).

Figure 4

Mean (±SEM) body weight, caloric intake, and water consumption of females did not vary as a function of creatine supplementation over 6 weeks (a–c). Separate one-way ANOVAs indicate that there were no differences in body weight (a), caloric intake (b), or water consumption (c) per week.

Figure 5

Mean (±SEM) latency to immobility (a), immobility counts (b, c), swimming counts (b, c), and climbing counts (b, c) of females as a function of creatine supplementation. Note that significance values displayed on graphs are derived from separate one-way ANOVAs for each FST trial compared with +0% controls. Repeated measures analyses indicate that (a, top panel) +4% creatine group displayed immobility less rapidly across trials compared with controls (^**p<0.001, +4 vs +0% p>0.05, +4 vs +2%). (b, c) Complementary pattern of results as measured by total immobility (*p=0.021, +4 vs +0% p>0.05, +4 vs +2%), swimming (^**p<0.001, +4 vs +0% p>0.05, +4 vs +2%), and climbing (n.s., all groups p>0.05). Data are presented as latencies to become immobile in seconds (a), or total counts of immobility, swimming, or climbing (b, c).

Figure 6

Mean (±SEM) wire suspension (a) and open field (b, c) performance of females as a function of creatine supplementation. One-way ANOVAs indicate that (c, bottom panel) anxiety-like behavior varied by diet. Females fed +4% creatine spent significantly less time in the corners compared with controls (^*p=0.016, +4 vs +0%) and significantly more time in the borders compared with animals fed +0 or +2% creatine (^*p=0.022, +4 vs +0% ^*p=0.044, +4 vs +2%), suggesting +4% creatine had a modest anxiolytic-like effect in females. Locomotion and muscle strength did not vary by diet (a–c). Data for time in center and latency to enter center are represented by a subset of the total number of rats (+0%: n=5; +2%: n=6; +4% n=5).