Regnier M, Herrera A A
Department of Biological Sciences, University of Southern California, Los Angeles 90089-2520.
J Neurobiol. 1993 Sep;24(9):1215-28. doi: 10.1002/neu.480240908.
Male frogs use their forelimb flexor muscles to clasp females during the mating behavior known as amplexus. We investigated the effects of testosterone on a principal forelimb flexor, the flexor carpi radialis muscle (FCR), using morphological and histochemical techniques. Male Xenopus laevis were surgically manipulated to produce high or low levels of circulating testosterone for an 8-week period. After this treatment, measurement of fibers in muscle cross-sections revealed that average fiber size was positively correlated with testosterone level. This effect was not the same for all muscle fibers, however. Fibers in the shoulder region were more sensitive to testosterone than fibers in other regions of the muscle. Histochemical staining of cross-sections showed that the patterns of staining for myosin ATPase or succinic dehydrogenase (SDH) were not influenced by testosterone levels, but total SDH activity was increased by testosterone treatment. When sensitivity to testosterone was correlated with ATPase activity, fibers with high ATPase activity were found to be more sensitive to testosterone than fibers with low activity, regardless of position within the muscle. Most fibers with high ATPase activity were located in the shoulder region of the muscle. These fibers are innervated by different motor axons than are fibers in the elbow region of the muscle, and contractions of shoulder (but not elbow) region fibers, elicited by stimulation of motor axons, are slowed by testosterone treatment (Regnier and Herrera, 1993, J. Physiol. 461:565-581).
在抱对这种交配行为中，雄性青蛙会用其前肢屈肌抱紧雌性。我们运用形态学和组织化学技术，研究了睾酮对主要前肢屈肌——桡侧腕屈肌（FCR）的影响。对雄性非洲爪蟾进行手术操作，使其在8周时间内维持高或低水平的循环睾酮。经过这种处理后，对肌肉横截面积中的纤维进行测量发现，平均纤维大小与睾酮水平呈正相关。然而，这种影响并非对所有肌肉纤维都相同。肩部区域的纤维比肌肉其他区域的纤维对睾酮更为敏感。横截面积的组织化学染色显示，肌球蛋白ATP酶或琥珀酸脱氢酶（SDH）的染色模式不受睾酮水平影响，但睾酮处理会增加SDH的总活性。当将对睾酮的敏感性与ATP酶活性相关联时，发现具有高ATP酶活性的纤维比低活性纤维对睾酮更敏感，无论其在肌肉中的位置如何。大多数具有高ATP酶活性的纤维位于肌肉的肩部区域。这些纤维由与肌肉肘部区域纤维不同的运动轴突支配，通过刺激运动轴突引发的肩部（而非肘部）区域纤维的收缩，会因睾酮处理而减缓（Regnier和Herrera，1993年，《生理学杂志》461:565 - 581）。
