Advances in modelling alpha-synuclein-induced Parkinson's diseases in rodents: Virus-based models versus inoculation of exogenous preformed toxic species.

Aggregates of alpha-synuclein (αSyn) have been described in Parkinson's disease (PD) patients, and recent evidence has suggested that the most toxic αSyn species in PD are small soluble aggregates including oligomers, prefibrils, protofibrils. The physiological function of αSyn is still highly debated, with a possible role in synaptic vesicle trafficking and release at the presynaptic compartment, and in the regulation of gene expression in the nucleus. Emerging evidence indicate that most of αSyn functions are related with the crucial ability to bind biological membranes, which is associated with structural conversion from a disordered monomer to an α-helical enriched structure. Conformational properties of αSyn can be modulated by a number of factors including post-translational modifications, gene duplication and triplication-driven overexpression, single point mutations, environmental changes, which affect membrane binding and the protein propensity to aggregate in toxic species. The recognized toxic role of αSyn in PD has laid the rational for purposing of αSyn-based, neuropathologically relevant preclinical models of PD. Different approaches have led to the establishment of transgenic models, viral vector-based models, and more recently models based on the intracerebral inoculation of exogenous αSyn preformed fibrils/oligomers. Here, we overview and compare viral vector-based models of αSyn overexpression and models obtained by direct intracerebral infusion of in vitro preformed αSyn species. The advantages and pitfalls associated with these different approaches are discussed.

Treatment with gut bifidobacteria improves hippocampal plasticity and cognitive behavior in adult healthy rats.

At the present time, gut microbiota inspires great interest in the field of neuroscience as a function of its role in normal physiology and involvement in brain function. This aspect suggests a specific gut-brain pathway, mainly modulated by gut microbiota activity. Among the multiple actions controlled by microbiota at the brain level, neuronal plasticity and cognitive function represent two of the most interesting aspects of this cross-talk communication. We address the possible action of two-months implementation of gut Bifidobacteria using a mixture of three different strains (B-MIX) on hippocampal plasticity and related cognitive behavior in adult healthy Sprague Dawley rats. B-MIX treatment increases the hippocampal BDNF with a parallel gain in dendritic spines' density of hippocampal CA1 pyramidal neurons. Electrophysiological experiments revealed a significant increment of HFS-induced LTP formation on the CA1 hippocampal region in B-MIX treated rats. All these effects are accompanied by a better cognitive performance observed in B-MIX treated animals with no impairments in locomotion activity. Therefore, in adult rats, the treatment with different strains of bifidobacteria is able to markedly enhance neuronal plasticity and the CNS function influencing cognitive behavior, an effect that may suggest a potential therapeutic treatment in brain diseases associated with cognitive functions.