Age, sex, and gonadal hormones differently influence anxiety- and depression-related behavior during puberty in mice

Abstract

Anxiety and depression symptoms increase dramatically during adolescence, with girls showing a steeper increase than boys after puberty onset. The timing of the onset of this sex bias led us to hypothesize that ovarian hormones contribute to depression and anxiety during puberty. In humans, it is difficult to disentangle direct effects of gonadal hormones from social and environmental factors that interact with pubertal development to influence mental health. To test the role of gonadal hormones in anxiety- and depression-related behavior during puberty, we manipulated gonadal hormones in mice while controlling social and environmental factors. Similar to humans, we find that mice show an increase in depression-related behavior from pre-pubertal to late-pubertal ages, but this increase is not dependent on gonadal hormones and does not differ between sexes. Anxiety-related behavior, however, is more complex during puberty, with differences that depend on sex, age, behavioral test, and hormonal status. Briefly, males castrated before puberty show greater anxiety-related behavior during late puberty compared to intact males, while pubertal females are unaffected by ovariectomy or hormone injections in all assays except the marble burying test. Despite this sex-specific effect of pubertal hormones on anxiety-related behavior, we find no sex differences in intact young adults, suggesting that males and females use separate mechanisms to converge on a similar behavioral phenotype. Our results are consistent with anxiolytic effects of testicular hormones during puberty in males but are not consistent with a causal role for ovarian hormones in increasing anxiety- and depression-related behavior during puberty in females.

Keywords: Anxiety; Depression; Gonadal hormones; Psychopathology; Puberty; Sex differences.

Fig. 1.. Peripubertal changes in anxiety- and depression-related behavior.

All bars are mean ± SEM. A) Separate groups of male and female mice were tested for anxiety- and depression-related behavior prior to puberty (P24–25) and during late puberty (P40–47). n=13 P24 females; n=11 P24 males; n=29 P40 females; n=23 P40 males. B) Time spent on the open arms of the EPM did not change with age, but P40 males spent more time in the open arms than P40 females. C) Time spent in the center of the open field did not change with age or differ between males and females. D) P40 mice spent more time immobile in the FST compared to P24 mice, with no difference between males and females. E) P40 mice buried more marbles than P24 mice, with no difference between males and females. **p<0.01 for main effect of age. *p<0.05 after Bonferroni correction for multiple comparisons.

Fig. 2.. Effects of pre-pubertal gonadectomy on anxiety- and depression-related behavior in late-pubertal mice.

All bars are mean ± SEM. A) Male and female mice underwent gonadectomy or sham surgery at P24, before puberty, and were tested for anxiety-related behavior at P40–47, during late puberty. n=15 ovariectomized (OVX) females; n=29 intact females; n=12 castrated (CAST) males; n=23 intact males. B) OVX did not affect EPM performance, but CAST males spent less time in the open arms compared to intact males, which resulted in a significant difference in the effect of gonadectomy between males and females. C) OVX did not affect open field performance, but CAST males showed a trend toward spending less time in the center of the open field compared to intact males. D) Gonadectomy did not affect FST performance in either sex. E) OVX decreased marble burying in females, while CAST had no effect, resulting in a significant difference in the effect of gonadectomy between males and females. #p<0.1; *p<0.05; **p<0.01; ***p<0.001; ****p<0.0001.

Fig. 3.. Induction of early-onset puberty in female mice does not alter anxiety- and depression-related behavior.

All bars are mean ± SEM. A) Female mice were injected with estradiol or vehicle on P24 and progesterone or vehicle on P26, a treatment that disinhibits the HPG axis and induces endogenous ovarian hormone release (Ramirez and Sawyer, 1965; Smith and Davidson, 1968). Hormone- and vehicle-treated mice were tested for anxiety- and depression-related behavior at P27–28, an age when vehicle-treated mice were still pre-pubertal. n=15 vehicle-treated mice; n=12 hormone-treated mice. Hormone treatment did not alter performance on the EPM (B), open field (C), FST (D), or marble burying test (E).

Fig. 4.. Young adult males and females do not differ in their performance on any behavior tested.

All bars are mean ± SEM. A) Gonadally intact, hormonally unmanipulated mice were tested for anxiety- and depression-related behavior post-pubertally (P69–83). n=15 females; n=10 males. Young adult male and female mice did not differ in their performance on the EPM (B), open field (C), FST (D), or marble burying test (E).