Neurochemical differences in two rat strains exposed to social isolation rearing

Abstract

Objective: Isolation rearing of rats provides a non-pharmacological method of inducing behavioural changes in rodents that resemble schizophrenia or depression. Nevertheless, results are variable within different strains. We focused on neurochemical changes in several in vivo and post-mortem brain regions of Wistar (W) and Lister Hooded (LH) rats following post-weaning social separation. Methods: Experiments were conducted after 6–8 weeks of isolation. For post-mortem studies, prefrontal cortex (PFC), nucleus accumbens (NAC), hippocampus (Hipp) and striatum (St) were collected by tissue dissection. In vivo experiments were conducted by microdialysis in the PFC. Analyses of dopamine (DA), serotonin (5-HT) levels and relative turnover were performed by using high-performance liquid chromatography. Results: We found significant strain-related differences in biogenic amine content. LH rats were characterised by markedly raised DA, along with its turnover reduction, in all the post-mortem brain regions examined as well as in microdialysis samples, while in W rats 5-HT tissue concentration was lower in PFC and St and higher in NAC and Hipp. Cortical extracellular 5-HT concentrations were increased in group housed and decreased in isolated W animals. Moreover, isolation increased DA concentrations in the PFC of LH rats, and decreased 5-HT in W rats in NAC and Hipp. Lately, 5-HT turnover was also affected by both strain and isolation conditions. Conclusions: This study suggests that W and LH rats have markedly different neurochemical profiles in response to isolation, resulting in altered monoamine levels that vary according to brain area and rat strain. These findings highlight the importance of selecting an appropriate rat strain when considering isolation rearing to model symptoms of schizophrenia and/or depression.