Fitch R H, Berrebi A S, Cowell P E, Schrott L M, Denenberg V H
Department of Psychology, University of Connecticut, Storrs 06269-4154.
Brain Res. 1990 May 7;515(1-2):111-6. doi: 10.1016/0006-8993(90)90584-x.
The rat's corpus callosum is sexually dimorphic, with the male's being larger. In addition, giving rats extra stimulation in infancy via handling increases callosal area in males, but not in females. To determine if this dimorphism is testosterone-dependent, male pups were castrated on Day 1 of life while females received an injection of testosterone propionate (TP) on Day 4. Control males had sham surgery and control females received an injection of sesame oil. All animals were handled daily from birth until weaning. Animals were sacrificed at 110 days and a mid-sagittal section of the callosum was obtained. From this section measures of callosal area, perimeter, length, and 99 widths were derived. We verified our previous finding that the male callosum is larger than that of the female. Neonatal TP treatment masculinized the callosa of the females, but castration did not affect the males. TP treatment affected the width dimension of the callosum but not callosal length or brain weight. In a related study the synthetic estrogen DES did not increase callosal size for castrated males or for intact females, while the estrogen blocker, tamoxifen, had a defeminizing effect on females' callosa. These findings suggest that there is an estrogen-dependent active process of feminization of cortical tissue in the female brain.
大鼠的胼胝体具有性别二态性，雄性的更大。此外，在幼年期通过抚摸给予大鼠额外刺激会增加雄性大鼠的胼胝体面积，但对雌性大鼠没有影响。为了确定这种二态性是否依赖于睾酮，雄性幼崽在出生第1天进行去势，而雌性幼崽在出生第4天注射丙酸睾酮（TP）。对照雄性大鼠进行假手术，对照雌性大鼠注射芝麻油。所有动物从出生到断奶每天都接受抚摸。在110天时处死动物，获取胼胝体的正中矢状切片。从该切片得出胼胝体面积、周长、长度和99个宽度的测量值。我们证实了之前的发现，即雄性的胼胝体比雌性的大。新生期TP处理使雌性大鼠的胼胝体雄性化，但去势对雄性大鼠没有影响。TP处理影响胼胝体的宽度维度，但不影响胼胝体长度或脑重量。在一项相关研究中，合成雌激素己烯雌酚对去势雄性大鼠或完整雌性大鼠的胼胝体大小没有增加作用，而雌激素阻断剂他莫昔芬对雌性大鼠的胼胝体有去雌性化作用。这些发现表明雌性大脑皮质组织存在依赖雌激素的主动雌性化过程。
