Tactile Learning within the Early Phase of Experimental Autoimmune Encephalomyelitis in Mice

Abstract

The purpose of this study was to assess tactile learning in the early phase of experimental autoimmune encephalomyelitis (EAE), which was induced in C57BL/6 mice by subcutaneous injections on flank of myelin oligodendrocyte glycoprotein, MOG35-55 (250 μg per mouse). Tactile learning was assessed one week after EAE induction using the novel object recognition test (NORT) in a dark room. The procedure consisted of two phases. During the training phase (T1), the animals explored two similar objects; within the test phase (T2, occurring 4 h later) the mice explored one novel and one familiar object. On average, mice developed significant behavioral disabilities related to EAE 13.2 ± 1.9 days following immunization. In the EAE group, the locomotor activity level (assessed by measuring the distance travelled) in the T1 and T2 phases did not differ significantly, as compared to the related phases in the control group (P > 0.05). Within phase T1, no reliable differences between experimental groups were found for the frequency (number) of visits to the sample objects and for total exploration time. For phase T2, no difference was also found in the discrimination ratio when comparing the control group with the EAE group. Our study demonstrates that tactile learning in male mice may not be affected 7 days after immunization with MOG35-55 (i.e., within the early EAE phase).