Olfactory Discrimination Deficits in A53T Alpha-Synuclein Transgenic Mice at 3 Months

Abstract

Abstract:Parkinson's disease (PD) is a kind of typical neurodegenerative diseases. Previously, clinical studies have showed that deficits in olfactory and cognitive functions precede motor-symptoms in PD. However, the mechanisms of olfactory discrimination deficits in early stage of PD is still unknown. In this study, we aimed to clarify the characteristics of olfactory deficits in A53T transgenic mice and test the possible mechanisms involved. By the elevated plus maze and bedding test, we showed that A53T transgenic mice at 3 months exhibit no hyperactivity behavior. Olfactory discrimination test indicated wild-type mice spent more time in old bedding than in new bedding during 5 min test (*P<0.05). However, the A53T transgenic mice could not distinguish between the old bedding and the new bedding at 3 months. In the fine odor discrimination test, we found that as the ratio [+] (Mango juice) to [-] (Almond juice) of odor components declined in task, the correct olfactory discriminations per trial session (%) reduced in A53T transgenic mice and wild type controls. There was no difference between two groups at the ratio of [+] 100:0 to [-] 0:100. However, at the ratio of [+] 60:40 to [-] 40:60, the correct olfactory discriminations per trial session (%) was significantly higher in control group. Rota-rod test indicated that A53T transgenic mice had no motor disorders. These findings reinforce the notion that the olfactory deficits occurred in early phase of PD, prior to motor disorder.