Neuroeffectors for vocalization in Xenopus laevis: hormonal regulation of sexual dimorphism.
Neuroeffectors for vocalization in Xenopus laevis: hormonal regulation of sexual dimorphism.
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DOI：
10.1002/neu.480170307
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发表时间：
1986-05
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影响因子：
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通讯作者：
Darcy B. Kelley
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文献类型：
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作者：
Darcy B. Kelley
南非爪蛙在求偶时会发出不同性别的叫声。男性的发声受性腺雄激素的控制。虽然雌性有中等水平的血液循环中的雄激素，但她们不会发出男性典型的配偶叫声。发声器官的肌肉和中枢神经系统(CNS)发声通路的神经元都是性二态的，对雄激素敏感。最近的研究表明，雄激素不能使成年女性男性化是男性特有的、雄激素调节的发育程序的结果。在变态时，喉是性单一的，在形态、肌纤维数量和雄激素受体含量上是女性的。在接下来的六个月里，在雄激素滴度和高受体水平的影响下，成肌细胞在男性体内增殖，肌纤维以平均每天100次的速度增加。雌性的荷尔蒙水平要低得多，感受器的值下降，而且她们没有表现出纤维的净增加。在变态过程中，雄性和雌性都有大约4000条肌肉纤维。成年后，男性的纤维数量是女性的8倍。在中枢神经系统中，成年喉运动神经元数量较多，胞体和树突较大，男性多于女性。发声通路中神经元的某些连接在女性中也不那么强健。与外周不同，运动神经元的数量似乎不是由雄激素诱导的增殖来确定的。我们目前的假设是，雄激素作用于喉肌肉水平，产生更多的肌肉纤维，从而为男性的运动神经元提供更多的靶点。这一过程可以通过个体发育细胞死亡来调节细胞数量。在中枢神经系统中，雄激素靶神经元在变态之前不久就能够积累激素。喉运动神经元中的雄激素受体可能通过增加对传入刺激的敏感性而允许男性的树突生长特征。这样的过程可以解释观察到的中枢神经系统发声“回路”的差异，从而解释性别之间的行为差异。
South African clawed frogs use sex-specific vocalizations during courtship. In the male, vocalizations are under the control of gonadal androgen. Though females have moderate levels of circulating androgen, they do not give male-typical mate calls. Both muscles of the vocal organ and neurons of the central nervous system (CNS) vocal pathway are sexually dimorphic and androgen-sensitive. Recent studies suggest that the failure of androgen to masculinize adult females results from a male-specific, androgen-regulated developmental program. At metamorphosis the larynx is sexually monomorphic and feminine in morphology, muscle fiber number and androgen receptor content. During the next six months, under the influence of increasing androgen titers and high receptor levels, myoblasts proliferate in the male and muscle fibers increase at an average rate of 100/day. Females have much lower hormone levels, receptor values decline and they display no net addition of fibers. At metamorphosis, both males and females have approximately 4000 muscle fibers. By adulthood, males have eight times the female fiber number. In the CNS, adult laryngeal motor neurons are more numerous with larger somata and dendritic trees in males than in females. Certain connections of neurons in the vocal pathway are also less robust in females. Unlike the periphery, motor neuron number does not appear to be established by androgen-induced proliferation. Our current hypothesis is that androgen acts at the level of laryngeal muscle to produce more muscle fibers and thus provide more target for motor neurons in the male. This process could regulate cell number by ontogenetic cell death. In the CNS, androgen-target neurons become capable of accumulating hormone shortly before metamorphosis. Androgen receptor in laryngeal motor neurons may permit the dendritic growth characteristic of males by increasing sensitivity to afferent stimuli. Such a process could account for the observed differences in CNS vocal "circuitry" in X. laevis and thus behavioral differences between the sexes.