Gonadectomy prior to puberty decreases normal parental behavior in adult mice

Abstract

Sex steroid hormones secreted by gonads influence development and expression of many behaviors including parental behaviors. The capacity to display many behaviors develops under the influence of sex steroid hormones; it begins with gonadal differentiation and lasts through puberty. The timing of gonadectomy may have important and long lasting effects on the organization and activation of neural circuits regulating the expression of different behaviors. The present study investigated the importance of exposure to endogenous gonadal steroid hormones during pubertal period/adolescence on parental behavior in adult mice. Male and female WT mice were gonadectomized either before puberty (25 days of age) or after puberty (60 days of age) and tested for parental behavior with and without estradiol benzoate (EB) replacement in adulthood. Additional groups of mice were gonadectomized at P25 and supplemented with estradiol (females) or testosterone (males) during puberty. Female mice gonadectomized after puberty or gonadectomized before puberty and supplemented with estradiol during puberty, displayed better pup directed parental behaviors in comparison to mice gonadectomized at 25 days of age regardless of treatment with estradiol in adulthood. However, mice treated with EB in adulthood displayed better non-pup directed nest building behavior than when they were tested without EB treatment regardless of sex and time of gonadectomy. To examine whether the sensitivity to sex steroid hormones was altered due to differences in time without gonads prior to the testing, mice were also tested for female sex behavior and there were no differences between mice gonadectomized at P25 or P60, although this could not completely rule out the possibility that parental behavior is more sensitive to prolonged absence of steroid hormones than female sex behavior. These results suggest that the absence of gonads and thereby the absence of appropriate gonadal steroid hormones during puberty/adolescence may have a profound effect on pup directed parental behaviors in adult mice.

Keywords: Gonadal hormones; Mice; Parental behavior; Puberty/adolescence.

Figure 1

Mice gonadectomized at P25 displayed reduced parental behavior in comparison to female mice gonadectomized at P60 and female mice gonadectomized at P25 and treated with EB during puberty in most parental behavior activities directed toward pups: a. latency to lift the first pup (^ap < 0.01; ^bp < 0.05), b. latency to the retrieval of the first pup into the nest (^ap < 0.01; ^bp < 0.05), c. number of retrieved pups into the nest (^ap < 0.01) and d. total time spent crouching over the pups (^ap < 0.01). Data are reported as mean + SEM; ^aSignificant difference between mice gonadectomized before puberty, after puberty, or mice gonadectomized before puberty and treated with EB during puberty. ^bSignificantly different from all three groups of males.

Figure 2

Mice without adult EB treatment displayed less nest building behavior than mice supplemented with EB in adulthood (during testing)regardless of sex or time of gonadectomy: a. total time spent building the nest (^ap < 0.01), b. the number of the time to initiate nest building (^ap < 0.05). Data are reported as mean + SEM. ^aSignificant difference between mice without and with EB treatment.

Figure 3

Female mice gonadectomized at P25 displayed similar lordosis quotient as females, gonadectomized at P60 after EB and progesterone treatment in adulthood. Data are reported as mean ± SEM.