SOCIAL ISOLATION AND ENVIRONMENTAL ENRICHMENT INDUCE CHANGES IN SYNAPTOPHYSIN AND GFAP LEVELS ALONG THE BRAIN-GUT AXIS OF RATS

Background: Social isolation (SI) may lead to numerous consequences. Studies with animal models have shown that environmental enrichment (EE) attenuates SI effects. Both SI and EE may induce changes in neurons and glial cells. Furthermore, recent studies suggest that SI and EE are linked to alterations in the gut-brain axis. This exploratory work aims to investigate if SI and EE induce synaptic and glial changes along the gut-brain axis.

Methods: Male and female Lister Hooded rats (postnatal day 21) were used. The rats are assigned in group-housed (3 rats per standard cage) or SI (1 rat per standard cage). After 4 weeks, the rats remain in these conditions or receive EE for 1 week, totalizing 4 groups: group-housed, EE, SI and enriched isolation. Samples from prefrontal cortex, hippocampus, spinal cord and large intestine are dissected for Western Blotting analysis. Synaptophysin and GFAP were measured as presynaptic and glial markers, respectively.

Results: Male rats exhibit higher average body weight and large intestine. Our preliminary results demonstrate that isolated rats exhibit reduction of fecal pellets in the large intestine and this is reversed by EE, suggesting functional changes. Similarly, results also suggest that SI reduces synaptophysin in females prefrontal cortex and this is reversed by EE. GFAP levels were increased in the prefrontal cortex and hippocampus of enriched isolated rats of both sexes. In the gut, results suggest increased synaptophysin in SI females. Furthermore, our preliminary results suggest that EE exerts opposite effects in GFAP in the gut of group-housed females and isolated males.

Conclusions: Ongoing studies are focused on clarifying the roles of SI and EE in gut-brain axis plasticity. Our initial results suggest that both interventions induce functional changes in the intestine, as well as in the central and enteric synaptic circuits in a sex-dependent manner.