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Thalamocortical synapses involving identified neurons in mouse primary somatosensory cortex: A terminal degeneration and golgi/EM study
Author(s) -
Hersch Steven M.,
White Edward L.
Publication year - 1981
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.901950206
Subject(s) - axon , neuron , synapse , neuroscience , biology , pyramidal cell , thalamus , golgi apparatus , somatosensory system , electron microscope , anatomy , dendritic spine , microbiology and biotechnology , physics , endoplasmic reticulum , hippocampal formation , optics
Abstract Synapses involving thalamocortical afferents and hitherto unexamined neuron types of the posteromedial barrel subfield (PMBSF) of the mouse have been identified using a combined degeneration and Golgi/EM technique (Peters et al., '77). Degeneration of thalamocortical axon terminals was produced with electrolytic lesions of the nucleus ventralis posterior, pars lateralis thalami, and the nucleus posterior thalami. Four days after receiving lesions, the animals were perfused, and blocks of cortex containing the PMBSF were processed by the Golgi method. The blocks were tissue‐chopped at 125 μm and examined with the light microscope. Sections containing neurons of interest were gold‐toned and deimpregnated in preparation for electron microscopy (Fairén et al., '77). Portions of selected neurons contained in layers III‐V were serially thin‐sectioned and examined with an electron microscope to determine if they were involved in synapses with degenerating thalamocortical axon terminals. Results showed thalamocortical synapses on the apical dendrites of five different sized pyramidal cells whose somata occurred in layers V and VI, and on dendrites of one spiny bitufted neuron and one non‐spiny multipolar neuron with somata in layer V. A non‐spiny bitufted neuron of layer IV which was not impregnated also received thalamocortical synapses. Although every neuron examined formed at least one thalamocortical synapse, some formed very few, whereas others formed many. Of the pyramidal cells, small layer V and VI pyramidal cells and a large deep layer V pyramidal cell were involved in small numbers of thalamocortical synapses, while a medium superficial layer V pyramidal cell and a large layer VI pyramidal cell each formed many. The spiny bitufted neuron formed a small number of thalamocortical synapses, while the non‐spiny bitufted neuron formed very many. The non‐spiny multipolar neuron was involved in a moderate number of thalamocortical synapses. The findings suggest that, whereas any type of neuron with a dendrite in layer IV likely receives some synaptic input from the thalamus, individual neurons were involved in very different quantities of thalamocortical synapses.