Exposure to an enriched environment promotes dendritic remodelling in hippocampal neurons affected by endogenous depression

Neuronal plasticity is enhanced in an enriched environment (EE) with more sensory and social interaction. In an animal model of endogenous depression, we have previously shown that EE has positive effects on spatial memory and hippocampus synaptic plasticity. However, nothing is known about how EE influences dendritic remodelling in hippocampal neurons affected by endogenous depression. In depressed rats, the impact of EE on hippocampus neuronal morphology was examined. Neonatal clomipramine exposure from postnatal days (PND) 8-21 days induced endogenous depression. The depressed-like rats were exposed to an enriched environment for two weeks in adulthood. Brains were then collected, stained with a modified Golgi-cox technique and, the hippocampal CA1 dendritic arborisation was evaluated using the Neurolucida software. Depression resulted in the atrophy of CA1 hippocampal neurons. The number of branching points and the overall number of dendritic intersections were reduced in depressed rats,. Exposure to an enriched environment significantly increased dendritic branching and the total number of dendritic intersections in hippocampal CA1 pyramidal neurons. The hippocampal pyramidal neuronal morphology of depressed rats improved after exposure to environmental enrichment. Neuronal plasticity and the development of novel therapeutic strategy will be improved by a greater understanding of how the environment affects neuronal morphology in depressed states.

Rapid and Sparse Labeling of Neurons Based on the Mutant Virus-Like Particle of Semliki Forest Virus / 神经科学通报·英文版

Sparse labeling of neurons contributes to uncovering their morphology, and rapid expression of a fluorescent protein reduces the experiment range. To achieve the goal of rapid and sparse labeling of neurons in vivo, we established a rapid method for depicting the fine structure of neurons at 24 h post-infection based on a mutant virus-like particle of Semliki Forest virus. Approximately 0.014 fluorescent focus-forming units of the mutant virus-like particle transferred enhanced green fluorescent protein into neurons in vivo, and its affinity for neurons in vivo was stronger than for neurons in vitro and BHK21 (baby hamster kidney) cells. Collectively, the mutant virus-like particle provides a robust and convenient way to reveal the fine structure of neurons and is expected to be a helper virus for combining with other tools to determine their connectivity. Our work adds a new tool to the approaches for rapid and sparse labeling of neurons in vivo.