Spatial and Working Memory Is Linked to Spine Density and Mushroom Spines.

Rasha Refaat Mahmmoud,Gert Lubec,Yogesh D Aher,Harald Höger,Maher Mokhtar,Sunetra Sase,Marion Gröger,Ajinkya Sase,Georges Chapouthier

doi:10.1371/journal.pone.0139739

Rasha Refaat Mahmmoud, Gert Lubec + Show 7 more

Open Access

https://doi.org/10.1371/journal.pone.0139739

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Abstract

BackgroundChanges in synaptic structure and efficacy including dendritic spine number and morphology have been shown to underlie neuronal activity and size. Moreover, the shapes of individual dendritic spines were proposed to correlate with their capacity for structural change. Spine numbers and morphology were reported to parallel memory formation in the rat using a water maze but, so far, there is no information on spine counts or shape in the radial arm maze (RAM), a frequently used paradigm for the evaluation of complex memory formation in the rodent.Methods24 male Sprague-Dawley rats were divided into three groups, 8 were trained, 8 remained untrained in the RAM and 8 rats served as cage controls. Dendritic spine numbers and individual spine forms were counted in CA1, CA3 areas and dentate gyrus of hippocampus using a DIL dye method with subsequent quantification by the Neuronstudio software and the image J program.ResultsWorking memory errors (WME) and latency in the RAM were decreased along the training period indicating that animals performed the task. Total spine density was significantly increased following training in the RAM as compared to untrained rats and cage controls. The number of mushroom spines was significantly increased in the trained as compared to untrained and cage controls. Negative significant correlations between spine density and WME were observed in CA1 basal dendrites and in CA3 apical and basal dendrites. In addition, there was a significant negative correlation between spine density and latency in CA3 basal dendrites.ConclusionThe study shows that spine numbers are significantly increased in the trained group, an observation that may suggest the use of this method representing a morphological parameter for memory formation studies in the RAM. Herein, correlations between WME and latency in the RAM and spine density revealed a link between spine numbers and performance in the RAM.

Highlights

Changes in synaptic structure that usually occur by activity have been proposed to underlie learning and memory
Spine numbers and morphology were reported to parallel memory formation in the rat using a water maze but, so far, there is no information on spine counts or shape in the radial arm maze (RAM), a frequently used paradigm for the evaluation of complex memory formation in the rodent
Working memory errors (WME) and latency in the RAM were decreased along the training period indicating that animals performed the task

Summary

Introduction

Changes in synaptic structure that usually occur by activity have been proposed to underlie learning and memory. Dendritic spines, which are specialized protrusions that form the site for excitatory synaptic contact, can undergo changes in size, shape and number in response to activity. Since learning effects are long-lasting, structural changes that occur to hippocampal synapses are supposed to correlate with spatial learning [1,2,3]. Many of the hippocampal synapses have plastic properties, which were proposed to play a vital role in the learning process [4].The hippocampus plays an important role in the declarative form of memory, which means retrieving daily facts and incidences[5, 6]. Changes in synaptic structure and efficacy including dendritic spine number and morphology have been shown to underlie neuronal activity and size. Spine numbers and morphology were reported to parallel memory formation in the rat using a water maze but, so far, there is no information on spine counts or shape in the radial arm maze (RAM), a frequently used paradigm for the evaluation of complex memory formation in the rodent

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