Abstract
Prelimbic cortex and infralimbic cortex, parts of the ventromedial prefrontal cortex, are critical brain regions for generating a flexible behavioral response to changing environmental contingencies. This includes the role of these brain structures in the extinction of learned fear, decision making and retrieval of remote memories. Dendritic structure of medial prefrontal cortex neurons retains significant structural plasticity in adulthood. This has been mainly demonstrated as dendritic atrophy and loss of dendritic spines due to chronic stress. It remains unknown if housing condition of the animals itself can cause opposing changes in the dendritic organization. In that backdrop, here we report that short-term increase in complexity of the housing causes a robust increase in complexity of dendritic architecture of prelimbic and infralimbic neurons. This is reflected in the dendritic expansion of prelimbic neurons and increase in spine density of prelimbic and infralimbic neurons. These results suggest that non-invasive changes in the housing environment can be harnessed to study brain reserves for the flexible and species-typical behaviors.
Highlights
Medial prefrontal cortex is a critical brain structure for mediation of flexible behaviors
Our choice of sub-regions in this study was guided by dichotomies between prefrontal cortex (PrL) and infralimbic neurons (IL) that are often observed during conditioned fear and drug seeking[15]
PrL is required for retrieval and expression of the conditioned fear in rats[16], while IL is needed for retention of subsequent fear extinction[17]
Summary
Medial prefrontal cortex is a critical brain structure for mediation of flexible behaviors. Chronic restraint stress results in approximately 20% reduction in total dendritic length of apical dendrites in medial prefrontal cortex neurons[5] This atrophy co-occurs with loss of spines by ≈16% relative to unstressed controls[6]. These numerical estimates suggest that chronic restraint can result in loss of around one-third of all spines in the medial prefrontal cortex; representing a significant retraction[6]. Exogenous corticosterone treatment causes atrophy and spine loss, in this case proximal dendrites are spared, and distal dendrites show more consistent effects[8,9] These studies suggest that prefrontal neurons in adulthood retain a capacity to undergo structural changes in response to the incipient stressful environment. We experimentally test this possibility by determining the effects of complex housing environment on dendritic architecture and spine density of prelimbic and infralimbic regions of the medial prefrontal cortex
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