Axon and dendrite geography predict the specificity of synaptic connections in a functioning spinal cord network.
Axon and dendrite geography predict the specificity of synaptic connections in a functioning spinal cord network.
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DOI：
10.1186/1749-8104-2-17
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发表时间：
2007-09-10
影响因子：
3.6
通讯作者：
Roberts A
中科院分区：
文献类型：
--
作者：
Li WC;Cooke T;Sautois B;Soffe SR;Borisyuk R;Roberts A
神经元网络发育时形成的突触连接有多具体？简单的规则能否解释功能回路的形成？这些问题是评估脊髓回路控制游泳的青蛙蝌蚪孵化。这是可能的，因为现在可以获得关于主要类型神经元的身份和突触连接的详细信息。通过对500对神经元进行电记录，直接测量了7种经鉴定的脊髓神经元之间的突触概率。对于相同的神经元类型，测量轴突和树突的背腹分布，然后用于计算轴突遇到特定树突并因此可能形成突触连接的概率。令人惊讶的是，在所有类型的神经元之间都发现了突触，但接触概率可以简单地通过轴突和树突的解剖学重叠来预测。这些结果表明，突触的形成可能不需要轴突来识别特定的正确树突。为了测试更简单的假设的可验证性，我们首先制作了能够生成纵向轴突生长路径并再现脊髓中发现的轴突分布模式和突触接触概率的计算模型。为了测试概率规则是否可以产生功能正常的脊髓网络，我们制作了脊髓神经元的真实计算模型，赋予它们既定的细胞特异性属性，并使用我们确定的接触概率将它们连接到网络中。这些网络中的大多数产生了强大的游泳活动。简单的因素，如控制背腹索马、树突和轴突位置的形态梯度，可以充分限制脊髓最初发育时不同类型神经元之间的突触连接，并允许功能网络形成。我们的分析表明，脊髓神经元类型之间的详细细胞识别可能不是必要的可靠的功能网络的形成，以产生早期的行为，如游泳。
How specific are the synaptic connections formed as neuronal networks develop and can simple rules account for the formation of functioning circuits? These questions are assessed in the spinal circuits controlling swimming in hatchling frog tadpoles. This is possible because detailed information is now available on the identity and synaptic connections of the main types of neuron. The probabilities of synapses between 7 types of identified spinal neuron were measured directly by making electrical recordings from 500 pairs of neurons. For the same neuron types, the dorso-ventral distributions of axons and dendrites were measured and then used to calculate the probabilities that axons would encounter particular dendrites and so potentially form synaptic connections. Surprisingly, synapses were found between all types of neuron but contact probabilities could be predicted simply by the anatomical overlap of their axons and dendrites. These results suggested that synapse formation may not require axons to recognise specific, correct dendrites. To test the plausibility of simpler hypotheses, we first made computational models that were able to generate longitudinal axon growth paths and reproduce the axon distribution patterns and synaptic contact probabilities found in the spinal cord. To test if probabilistic rules could produce functioning spinal networks, we then made realistic computational models of spinal cord neurons, giving them established cell-specific properties and connecting them into networks using the contact probabilities we had determined. A majority of these networks produced robust swimming activity. Simple factors such as morphogen gradients controlling dorso-ventral soma, dendrite and axon positions may sufficiently constrain the synaptic connections made between different types of neuron as the spinal cord first develops and allow functional networks to form. Our analysis implies that detailed cellular recognition between spinal neuron types may not be necessary for the reliable formation of functional networks to generate early behaviour like swimming.
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影响因子：
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