Ih Equalizes Membrane Input Resistance in a Heterogeneous Population of Fusiform Neurons in the Dorsal Cochlear Nucleus

Cesar C. Ceballos, Shuang Li, Antonio C. Roque, Thanos Tzounopoulos and Ricardo M. Leão

In a neuronal population, several combinations of its ionic conductances are used to attain a specific firing phenotype. Some neurons present heterogeneity in their firing, generally produced by expression of a specific conductance, but how additional conductances vary along in order to homeostatically regulate membrane excitability is less known. Dorsal cochlear nucleus principal neurons, fusiform neurons, display heterogeneous spontaneous action potential activity and thus represent an appropriate model to study the role of different conductances in establishing firing heterogeneity. Particularly, fusiform neurons are divided into quiet, with no spontaneous firing, or active neurons, presenting spontaneous, regular firing. These modes are determined by the expression levels of an intrinsic membrane conductance, an inwardly rectifying potassium current (IKir). In this work, we tested whether other subthreshold conductances vary homeostatically to maintain membrane excitability constant across the two subtypes. We found that Ih expression covaries specifically with IKir in order to maintain membrane resistance constant. The impact of Ih on membrane resistance is dependent on the level of IKir expression, being much smaller in quiet neurons with bigger IKir, but Ih variations are not relevant for creating the quiet and active phenotypes. Finally, we demonstrate that the individual proportion of each conductance, and not their absolute conductance, is relevant for determining the neuronal firing mode. We conclude that in fusiform neurons the variations of their different subthreshold conductances are limited to specific conductances in order to create firing heterogeneity and maintain membrane homeostasis.

Random Structures in the Brain (workshop)

The Research, Innovation and Dissemination Center for Neuromathematics (NeuroMat) will hold the workshop “Random Structures in the Brain” in São Paulo, from October 16 to 20, 2017. NeuroMat is hosted by the University of São Paulo and funded by the São Paulo Research Foundation (FAPESP).

Video presentation of ABRAÇO

Video of the NeuroMat network on the brachial plexus injury, ABRAÇO.

Aiming at new possibilities for the diagnosis of Parkinson's Disease

A NeuroMat-led initiative has aimed at developing a new tool for early diagnosis of Parkinson's Disease. This initiative relies on a game to identify behaviorial patterns associated to this disease in a cost efficient way. Parkinson's Disease is a degenerative disorder of the nervous system and affects 1% of the world population of over 65 years, according to the Association Brazil Parkinson. This work is part of the NeuroMat-led network AMPARO.

An almost virtual museum

The NeuroMat dissemination team has led the release of images from museums at the University of São Paulo to an open media repository, and this initiative has now been started with the Paulista Museum. Eduardo Nunomura, Carta Capital, 9/13/2017.

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The Research, Innovation and Dissemination Center for Neuromathematics is hosted by the University of São Paulo and funded by FAPESP (São Paulo Research Foundation).

 

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