Agmon A, Connors B W
Department of Neurology, Stanford University School of Medicine, CA 94305.
Neuroscience. 1991;41(2-3):365-79. doi: 10.1016/0306-4522(91)90333-j.
We have developed a novel slice preparation of the mouse somatosensory forebrain. This preparation is unique in including both the ventrobasal nucleus of the thalamus and the sensorimotor "barrel" cortex in a 400-microns-thick slice with the functional connectivity between them preserved, and in allowing direct visualization of the various components of the barrel system in unstained living tissue. Thalamocortical connectivity was demonstrated by recording the laminar profile of cortical field potentials evoked electrically from the ventrobasal nucleus. Current-source density analysis of this profile showed that the largest and earliest sinks were coextensive with the two known sites of thalamocortical terminals, layer IV and the junction of layers V and VI. The sink in layer IV could be dissociated experimentally into a small, early sink of presynaptic origin (most probably a presynaptic spike volley in the thalamocortical terminals) and a later, larger sink generated postsynaptically. By mapping the subcortical stimulation sites that elicited a response at different layer IV recording sites we concluded that the thalamus-to-cortex projection preserves the general dorsoventral relationship of the afferents. Intracellularly recorded responses elicited by thalamic stimulation included (but were not limited to) monosynaptic excitatory and disynaptic inhibitory postsynaptic potentials. The thalamus-to-cortex connections were also mapped with the axonal fluorescent tracer dioctadecyl-tetramethylindocarbocyanine perchlorate. The thalamo-cortical slice is a very suitable system for studying the physiology and pharmacology of the thalamocortical synapse and for exploring the synaptic circuitry of the somatosensory cortex.
我们开发了一种新型的小鼠体感前脑切片制备方法。这种制备方法的独特之处在于，在一个400微米厚的切片中同时包含丘脑腹侧基底核和感觉运动“桶状”皮层，并且保留了它们之间的功能连接，还能直接观察未染色活组织中桶状系统的各个组成部分。通过记录从腹侧基底核电刺激诱发的皮层场电位的分层分布，证实了丘脑皮质连接。对该分布进行电流源密度分析表明，最大和最早的电流汇与丘脑皮质终末的两个已知部位，即IV层以及V层和VI层交界处，范围一致。IV层中的电流汇在实验上可分解为一个小的、早期的突触前起源电流汇（很可能是丘脑皮质终末的突触前峰电位群）和一个后期的、更大的突触后产生的电流汇。通过绘制在不同IV层记录部位引发反应的皮层下刺激位点，我们得出结论，丘脑到皮层的投射保留了传入纤维的一般背腹关系。丘脑刺激诱发的细胞内记录反应包括（但不限于）单突触兴奋性和双突触抑制性突触后电位。还使用轴突荧光示踪剂二辛基十四甲基吲哚碳菁高氯酸盐绘制了丘脑到皮层的连接。丘脑皮质切片是研究丘脑皮质突触的生理学和药理学以及探索体感皮层突触回路的非常合适的系统。
