Testosterone implants into the amygdala during the neonatal period masculinize the social play of juvenile female rats

doi:10.1016/0006-8993(86)91492-7

Brain Research

Volume 398, Issue 2, 29 November 1986, Pages 324-328

https://doi.org/10.1016/0006-8993(86)91492-7 Get rights and content

The masculinization of social play behavior in the rat is dependent upon the actions of androgens during the neonatal period. The amygdala, a major androgen-target region in the rat limbic brain, appears to be a critical site for this androgenic effect. We tested this hypothesis by implanting testosterone-bearing cannulae into the amygdal a of female rat pups on Day 1 of life; the implants were removed on Day 8 of life. The animals were then observed daily between Days 26 and 40 of life and the frequency of play-fighting was recorded. Testosterone-implanted females, like normal males, engaged in significantly more play-fighting than did control females (implanted with cholesterol-bearing cannulae). We have also prevented data indicating that the testosterone diffusion from the cannulae was, for the most part, restricted to the amygdala. Thus, testosterone implanted into the amygdala mimicked the effects previously reported for systemic testosterone injections, supporting the idea that the amygdala is a critical region for the actions of androgens on the sexual differentiation of social play behavior in the rat.

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Citation Excerpt :
Together, these observations led to the hypothesis that testosterone-dependent sexual differentiation of the amygdala during the perinatal period is critical in establishing a sex difference in levels of juvenile play fighting. Accordingly, introducing testosterone directly into the medial amygdala of female pups is sufficient to induce male-like amounts of play behavior in juvenile females (Meaney and McEwen, 1986). What kinds of sex differences in the amygdala could underlie sex differences in juvenile play fighting?
Understanding how sex differences in innate animal behaviors arise has long fascinated biologists. As a general rule, the potential for sex differences in behavior is built by the developmental actions of sex-specific hormones or regulatory proteins that direct the sexual differentiation of the nervous system. In the last decade, studies in several animal systems have uncovered neural circuit mechanisms underlying discrete sexually dimorphic behaviors. Moreover, how certain hormones and regulatory proteins implement the sexual differentiation of these neural circuits has been illuminated in tremendous detail. Here, we discuss some of these mechanisms with three case-studies—mate recognition in flies, maturation of mating behavior in worms, and play-fighting behavior in young rodents. These studies illustrate general and unique developmental mechanisms to establish sex differences in neuroanatomy and behavior and highlight future challenges for the field.

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Testosterone implants into the amygdala during the neonatal period masculinize the social play of juvenile female rats

Anal. Biochem.

Horm. Behav.

Brain Research

Anim. Behav.

Horm. Behav.

Physiol. Behav.

Dev. Brain Res.

Physiol. Behav.

Temporal boundary of the sensitive period for hormonal organization of social play in juvenile rats

Physiol. Behav.

Rough-and-tumble play among nursery school children

Perinatal hormones and their role in the development of sexually dimorphic behaviors

Estrogen and androgen receptor proteins in embryonic and neonatal brain, hypothesis for sexual differentiation of behavior

Am. Zool.

Early hormonal influences on the development of sexual and sex-related behavior