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Ultrastructural and optogenetic dissection of V1 corticotectal terminal synaptic properties.

A new interesting article has been published in J Comp Neurol. 2018 Sep 26. doi: 10.1002/cne.24538. and titled:

Ultrastructural and optogenetic dissection of V1 corticotectal terminal synaptic properties.

Authors of this article are:
Masterson SP Zhou N Akers BK Dang W Bickford ME.

A summary of the article is shown below:
The superior colliculus (SC) is a major site of sensorimotor integration in which sensory inputs are processed to initiate appropriate motor responses. Projections from the primary visual cortex (V1) to the SC have been shown to exert a substantial influence on visually-induced behavior, including “freezing”. However, it is unclear how V1 corticotectal terminals affect SC circuits to mediate these effects. To investigate this, we used anatomical and optogenetic techniques to examine the synaptic properties of V1 corticotectal terminals. Electron microscopy revealed that V1 corticotectal terminals labeled by anterograde transport primarily synapse (93%) on dendrites that do not contain gamma amino butyric acid (GABA). This preference was confirmed using optogenetic techniques to photoactivate V1 corticotectal terminals in slices of the SC maintained in vitro. In a mouse line in which GABAergic SC interneurons express green fluorescent protein (GFP), few GFP-labeled cells (11%) responded to activation of corticotectal terminals. In contrast, 67% of nonGABAergic cells responded to activation of V1 corticotectal terminals. Biocytin-labeling of recorded neurons revealed that wide-field vertical (WFV) and non-WFV cells were activated by V1 corticotectal inputs. However, WFV cells were activated in the most uniform manner; 85% of these cells responded with excitatory postsynaptic potentials (EPSPs) that maintained stable amplitudes when activated with light trains at 1-20HZ. In contrast, in the majority of non-WFV cells, the amplitude of evoked EPSPs varied across trials. Our results suggest that V1 corticotectal projections may initiate freezing behavior via uniform activation of the WFV cells, which project to the pulvinar nucleus. This article is protected by copyright. All rights reserved.

Check out the article’s website on Pubmed for more information:

This article is a good source of information and a good way to become familiar with topics such as: GABA;GAD67;RRID: nif-000-30467;RRID:AB_10015246;RRID:AB_477652;RRID:AB_91337;channelrhodopsin;electron microscopy;excitatory postsynaptic potential;superior colliculus;synapse;widefield vertical.

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