Self-Structuring of Motile Astrocytic Processes within the Network of a Single Astrocyte

Dynamic structuring and functions of perisynaptic astrocytic processes and of the gap junction network within a single astrocyte are outlined. Motile perisynaptic astrocytic processes are generating microdomains. By contacting and retracting of their endfeet an appropriate receptor pattern is selected that modulates the astrocytic receptor sheath for its activation by neurotransmitter substances, ions, transporters, etc. This synaptic information processing occurs in three distinct time scales of milliseconds to seconds, seconds to minutes, hours or longer. Simultaneously, the interconnecting gap junctions are activated by building a network within the astrocyte. Frequently activated gap junction cycles become embodied in gap junction plaques. The gap junction network formation and gap junction plaques are governed and controlled in the same time scales as synaptic information processing. Biomimetic computer systems may represent an alternative to limitations of brainphysiological research. The model proposed allows the interpretation of affective psychoses and schizophrenia as time disorders basically determined by a shortened, prolonged or lacking time scale of synaptic information processing.

Lesion-induced changes of brevican expression in the perineuronal net of the superior vestibular nucleus

Damage to the vestibular sense organs evokes static and dynamic deficits in the eye movements,posture and vegetative functions.After a shorter or longer period of time,the vestibular function is partially or completely restored via a series of processes such as modification in the efficacy of synaptic inputs.As the plasticity of adult central nervous system is associated with the alteration of extracellular matrix,including its condensed form,the perineuronal net,we studied the changes of brevican expression in the perineuronal nets of the superior vestibular nucleus after unilateral labyrinth lesion.Our results demonstrated that the unilateral labyrinth lesion and subsequent compensation are accompanied by the changing of brevican staining pattern in the perineuronal nets of superior vestibular nucleus of the rat.The reduction of brevican in the perineuronal nets of superior vestibular nucleus may contribute to the vestibular plasticity by suspending the non-permissive role of brevican in the restoration of perineuronal net assembly.After a transitory decrease,the brevican expression restored to the control level parallel to the partial restoration of impaired vestibular function.The bilateral changing in the brevican expression supports the involvement of commissural vestibular fibers in the vestibular compensation.All experimental procedures were approved by the 'University of Debrecen–Committee of Animal Welfare'(approval No.6/2017/DEMAB) and the 'Scientific Ethics Committee of Animal Experimentation'(approval No.HB/06/éLB/2270-10/2017;approved on June 6,2017).

The adjustment of γ-aminobutyric acid_A tonic subunits in Huntington＇s disease：from transcription to translation to synaptic levels into the neostriatum

γ-Aminobutyric acid（GABA）,plays a key role in all stages of life,also is considered the main inhibitory neurotransmitter.GABA activates two kind of membrane receptors known as GABAA and GABAB,the first one is responsible to render tonic inhibition by pentameric receptors containing α4-6,β3,δ,or ρ1-3 subunits,they are located at perisynaptic and/or in extrasynaptic regions.The biophysical properties of GABAA tonic inhibition have been related with cellular protection against excitotoxic injury and cell death in presence of excessive excitation.On this basis,GABAA tonic inhibition has been proposed as a potential target for therapeutic intervention of Huntington＇s disease.Huntington＇s disease is a neurodegenerative disorder caused by a genetic mutation of the huntingtin protein.For experimental studies of Huntington＇s disease mouse models have been developed,such as R6/1,R6/2,Hdh Q92,Hdh Q150,as well as YAC128.In all of them,some key experimental reports are focused on neostriatum.The neostriatum is considered as the most important connection between cerebral cortex and basal ganglia structures,its cytology display two pathways called direct and indirect constituted by medium sized spiny neurons expressing dopamine D1 and D2 receptors respectively,they display strong expression of many types of GABAA receptors,including tonic subunits.The studies about of GABAA tonic subunits and Huntington＇s disease into the neostriatum are rising in recent years,suggesting interesting changes in their expression and localization which can be used as a strategy to delay the cellular damage caused by the imbalance between excitation and inhibition,a hallmark of Huntington＇s disease.