Difference of relay modes in synaptic organization of the somatic and visceral thalamic nuclei.

我们用光镜和电子显微镜观察了丘脑的体核和内脏核，以了解它们的突触组织特征。腹外侧核(VL)和腹前核(VA)是运动核团，膝状体内侧核(MGN)是感觉核，丘脑室旁核(PVT)是内脏核。超薄切片三维重建显示，小脑终末(CLRs)主要与丘脑皮质投射神经元(TCNs)的初级和次级树突进行突触接触，而皮质终末则在远侧树突上形成突触。内源性神经元的突触前树突(PSD)和来源不明的轴突终末(Ps)在树突和神经元胞体的每一级上形成突触。并对CLR、TCN树突和PSD形成的突触复合体(突触三联体)进行了分析。属于P的丘脑网状核(TRN)的终末独立于突触三联体。在VA，内侧单核终末主要与TCNs的胞体和初级树突进行突触接触。此外，还观察到ELP、TCN树突和PSD之间的突触三联体。由于ELP在本质上是抑制性的，PSD可能对TCN.TRN起抑制作用，VA内的TRN终末通常表现为与ELP的突触后或带有圆形小泡的终末的连续突触。在本研究中，我们准确地研究了听觉相关皮质区域与MGN亚核之间的关系。关于PVT，我们证明了被称为排尿中心的Barrington核中的神经元通过轴突侧支将轴突发送到脊髓和PVT。我们还观察到许多PVT神经元通过侧支向边缘皮质和伏核发出轴突。

We observed light and electron microscopically somatic and visceral thalamic nuclei to know their characteristics of the synaptic organization. Wechose the ventral lateral (VL) and ventral anterior (VA) nuclei as the motor, the medial geniculate nucleus (MGN) as the sensory and the paraventricular thalamic nucleus (PVT) as the visceral nuclei.In the VL,three-dimensional reconstruction from serial ultrathin sections revealed that cerebellar terminals (CLRs) predominantly made synaptic contacts on primary and secondary dendrites of thalamocortical projection neurons (TCNs), whereas, cortical terminals made synapses on distal dendrites. Presynaptic dendrites (PSDs) of intrinsic neurons and axon terminals of unidentified origins (Ps) made synapses on every order of dendrites and neuronal somata. The synaptic complex (synaptic triad), formed by the CLR,dendrites of the TCN and the PSD was also analyzed. Terminals from the thalamic reticular nucleus (TRN), which belong to P were located independently from the synaptic triad. In the VA,entopeduncular terminals (ELPs) mainly made synaptic contacts with somata and primary dendrites of TCNs. The synaptic triad among the ELP,TCN dendrites and PSD was also observed. Because the ELP is inhibitory in nature, the PSD may play a role of disinhibition against the TCN.TRN terminals in the VA often showed serial synapses in which they were posynaptic to ELPs or terminals with round vesicles.We studied the corticocortical connections to know the morphological bases of auditory information processing. During this study we examined the relationship between auditory related cortical areas and the subnuclei of the MGN precisely.About the PVT,we proved that neurons in the Barrington's nucleus which is known as the micturition center sent axons to both the spinal cord and the PVT by axon collaterals. We also observed that many PVT neurons gave off axons to both the limbic cortex and nucleus accumbens by collaterals.