Sogol Meknatkhah - Institute of Biochemistry and Biophysics (IBB), University of Tehran, Tehran, Iran
Monireh-Sadat Mousavi - Institute of Biochemistry and Biophysics (IBB), University of Tehran, Tehran, Iran
Pouya Sharif Dashti - Department of Chemical Engineering, University of Tehran, Tehran, Iran
Gholam Hossein Riazi - Institute of Biochemistry and Biophysics (IBB), University of Tehran, Tehran, Iran

Background and Aim : Considering the increasingly stressful lifestyles and the frequency of day-to-day emotional disturbance in modern societies, numerous studies have focused on the effects of stress as an important risk factor in progression or even in the onset of many disorders such as Multiple Sclerosis. In this study, the effect of psychological and physical stress concerning myelin degradation was investigated. The spatial working memory assessment as evidence of brain demyelination severity in response to stress exposure in the cuprizone-induced model of Multiple Sclerosis was investigated and the response related to the demyelination extremity.Methods : healthy female Wistar rats were randomly divided into 4 groups (i.e. control group (Cont), non-stress cuprizone treated (N-CPZ), physical stress- cuprizone treated (P-CPZ) and emotional stress- cuprizone treated (E-CPZ), n=7 per group. At 5 weeks of age, a witness stress foot-shock paradigm was used to induce stress for 5 days. Followed by demyelination through 6 weeks of cuprizone administration, the Y-maze test was performed to assess the spatial working memory.Results : proportional to the Y-maze task analysis, both P-CPZ and E-CPZ groups revealed more impaired spatial memory compared to the N-CPZ group (p <0.01). Importantly, spatial memory deficiency was remarkable in the E-CPZ group (p <0.01).Conclusion : the oligodendrocyte death, the disintegration of the myelin sheath and consequently neurodegeneration leads to memory deficit and locomotion impairment. It is reflected by lower scores on the novel arm visits in the Y-maze test. Severe degeneration in both E-CPZ and P-CPZ groups, particularly the E-CPZ rats, reveals the deteriorating impacts of the background stress.

Stress; Demyelination; Working memory; Y- maze