Enriched phenotype analysis: Tying perineuronal net structures to high and low burrowers in isolated and enrichedly housed rats

Affective state has influence over behaviour and cognition. A negative affective state compromises health and immune response. The extracellular matrix, a lesser understood region of the brain, potentially provides mechanisms for change in mood states. Mood disorders associate with change in plasticity; specifically, perineuronal nets (PNNs) associate with synaptic plasticity. PNNs mostly surround Parvalbumin neurons (PV) thereby altering inhibitory signalling.The aim of this study was to induce a positive or negative affective state in rats through housing conditions, validate this with behavioural tests, and explore structural changes of PNNs in the rat brain. Adult rats were housed singly isolated or caged together in enriched environments for 21 days ( n=12 per group) to induce a shift in affective state. Brain tissue was analysed by immunofluorescent labelling of PNNs with Wisteria floribunda agglutinin staining.Results of the burrowing task showed a change in behaviour was induced at day 3 (p<0.0001) and day 21 (p=0.042) (Mann Whitney U-test). For initial analysis, the top two high and low burrowers in each group were analysed for PNNs and PV in the anterior cingulate cortex as this region is involved in processing emotions and behaviour regulation. However, there was no significant difference found in PNN count, PV count or colocalization of PNN and PV within this region. Limited research exists on functional causality of PNNs on behaviour and cognition. Day 3 showed the greatest change in behaviour so any molecular changes at this timepoint may have been missed. Further analysis will be undertaken.