Cox C L, Zhou Q, Sherman S M
Department of Neurobiology, State University of New York, Stony Brook 11794-5230, USA.
Nature. 1998 Jul 30;394(6692):478-82. doi: 10.1038/28855.
The relay of information through thalamus to cortex is dynamically gated, as illustrated by the retinogeniculocortical pathway. Important to this is the inhibitory interneuron in the lateral geniculate nucleus (LGN). For the typical neuron, synaptic information arrives through postsynaptic dendrites and is transmitted by axon terminals. However, the typical thalamic interneuron, in addition to conventional axonal outputs, has distal dendrites that serve both pre- and postsynaptic roles. These dendritic terminals participate in curious and enigmatic triadic arrangements, in which each contacts a relay cell dendrite and is contacted by a glutamatergic retinal terminal that innervates the same relay cell dendrite. Here we show that agonists of the metabotropic glutamate receptor (mGluR) activate dendritic terminals of interneurons in the absence of action potentials, thereby inhibiting the postsynaptic relay neuron. Somatic recordings from LGN interneurons reveal that there is no response to mGluR agonists, suggesting that their dendritic terminals are electrically isolated from their somata and axons, consistent with anatomical modelling of these cells. Our results offer insight into the functioning of triadic circuitry and indicate that thalamic interneurons can perform independent computations expressed through axonal as opposed to dendritic outputs.
信息通过丘脑向皮层的传递是动态控制的，视网膜-膝状体-皮层通路就说明了这一点。对此至关重要的是外侧膝状体核（LGN）中的抑制性中间神经元。对于典型的神经元，突触信息通过突触后树突传入，并由轴突终末传出。然而，典型的丘脑中间神经元除了常规的轴突输出外，还有起突触前和突触后作用的远端树突。这些树突终末参与奇特而神秘的三联体结构，其中每个终末都与一个中继细胞树突接触，并被一个支配同一中继细胞树突的谷氨酸能视网膜终末所接触。我们在此表明，代谢型谷氨酸受体（mGluR）激动剂在没有动作电位的情况下激活中间神经元的树突终末，从而抑制突触后中继神经元。对LGN中间神经元的体细胞记录显示，对mGluR激动剂无反应，这表明它们的树突终末在电上与其胞体和轴突隔离，这与这些细胞的解剖学模型一致。我们的结果为三联体电路的功能提供了见解，并表明丘脑中间神经元可以通过轴突输出而非树突输出进行独立计算。
