Wade J, Crews D
Department of Psychology, University of Texas, Austin 78712.
J Comp Neurol. 1991 Jul 22;309(4):507-14. doi: 10.1002/cne.903090407.
The anterior hypothalamus-preoptic area and ventromedial hypothalamus are sexually dimorphic in the reproductively active whiptail lizard Cnemidophorus inornatus. The anterior hypothalamus-preoptic area, which is involved in the control of male-typical copulatory behaviors, is larger in males, whereas the ventromedial hypothalamus, which is involved in the control of female-typical receptivity, is larger in females. In the parthenogenetic whiptail lizard C. uniparens, which is a direct descendant of C. inornatus and exhibits both male-like and female-like pseudosexual behaviors, both brain areas are comparable in size to those of female C. inornatus. This study was conducted to determine whether these brain areas change in size in either species or sex during a time of year when these animals are reproductively inactive, or after removal of the gonads. In male C. inornatus both brain areas changed during reproductive inactivity (either seasonally or surgically induced) and became equivalent to the size characteristic of reproductively active female C. inornatus. When corrected for brain size, the anterior hypothalamus-preoptic area was significantly smaller in intact hibernating and castrated males than in intact males from the summer breeding season. Conversely, the ventromedial hypothalamus was significantly larger in intact hibernating and castrated males than in intact males from the summer breeding season. The two brain areas were not significantly different among the groups of female C. inornatus or parthenogenetic C. uniparens. These results suggest that 1) the brain of whiptail lizards may differentiate seasonally and 2) the female state may be a neutral one to which the male brain reverts during reproductive inactivity.
在具有繁殖活性的无饰鞭尾蜥中，下丘脑前视前区和下丘脑腹内侧核具有性别二态性。参与控制雄性典型交配行为的下丘脑前视前区在雄性中较大，而参与控制雌性典型接受性的下丘脑腹内侧核在雌性中较大。在孤雌生殖的鞭尾蜥单性生殖鞭尾蜥中，它是无饰鞭尾蜥的直接后代，表现出类似雄性和雌性的假性行为，这两个脑区的大小与无饰鞭尾蜥雌性的相当。本研究旨在确定在这些动物繁殖不活跃的一年中的某个时期，或者在摘除性腺后，这两个脑区在这两个物种或性别中是否会发生大小变化。在无饰鞭尾蜥雄性中，这两个脑区在繁殖不活跃期间（无论是季节性的还是手术诱导的）都会发生变化，并变得与具有繁殖活性的无饰鞭尾蜥雌性的大小特征相当。校正脑大小后，完整冬眠和阉割雄性的下丘脑前视前区明显小于夏季繁殖季节的完整雄性。相反，完整冬眠和阉割雄性的下丘脑腹内侧核明显大于夏季繁殖季节的完整雄性。在无饰鞭尾蜥雌性或孤雌生殖的单性生殖鞭尾蜥组中，这两个脑区没有显著差异。这些结果表明：1）鞭尾蜥的大脑可能会随季节分化；2）雌性状态可能是一种中性状态，雄性大脑在繁殖不活跃时会恢复到这种状态。
