Winer J A, Larue D T
Division of Neurobiology, Departmwnt of Molecular and Cell Biology, University of California, Berkeley 94720-3200, USA.
Proc Natl Acad Sci U S A. 1996 Apr 2;93(7):3083-7. doi: 10.1073/pnas.93.7.3083.
Many features in the mammalian sensory thalamus, such as the types of neurons, their connections, or their neurotransmitters, are conserved in evolution. We found a wide range in the proportion of gamma-aminobutyric acidergic (GABAergic) neurons in the medial geniculate body, from <1% (bat and rat) to 25% or more (cat and monkey). In the bat, some medial geniculate body subdivisions have no GABAergic cells. Species-specific variation also occurs in the somesthetic ventrobasal complex. In contrast, the lateral geniculate body of the visual system has about the same proportion of GABAergic cells in many species. In the central auditory pathway, only the medial geniculate body shows this arrangement; the relative number of GABAergic cells in the inferior colliculus and auditory cortex is similar in each species. The range in the proportion of GABAergic neurons suggests that there are comparative differences in the neural circuitry for thalamic inhibition. We conclude that the number of GABAergic neurons in thalamic sensory nuclei may have evolved independently or divergently in phylogeny. Perhaps these adaptations reflect neurobehavioral requirements for more complex, less stereotyped processing, as in speech-like communication.
哺乳动物感觉丘脑的许多特征，如神经元类型、它们的连接方式或神经递质，在进化过程中是保守的。我们发现内侧膝状体中γ-氨基丁酸能（GABA能）神经元的比例范围很广，从<1%（蝙蝠和大鼠）到25%或更高（猫和猴子）。在蝙蝠中，一些内侧膝状体亚区没有GABA能细胞。躯体感觉腹侧基底复合体也存在物种特异性变异。相比之下，视觉系统的外侧膝状体在许多物种中的GABA能细胞比例大致相同。在中枢听觉通路中，只有内侧膝状体呈现这种分布；每个物种中，下丘和听觉皮层中GABA能细胞的相对数量相似。GABA能神经元比例的范围表明丘脑抑制的神经回路存在比较差异。我们得出结论，丘脑感觉核中GABA能神经元的数量可能在系统发育中独立或发散地进化。也许这些适应性反映了对更复杂、较少刻板加工的神经行为需求，比如在类似语音的交流中。
