Chronic agomelatine treatment alleviates icvAβ-induced anxiety and depressive-like behavior through affecting Aβ metabolism in the hippocampus in a rat model of Alzheimer's disease.

Recently, we reported that the atypical antidepressant agomelatine (Ago) exerted a beneficial impact on behavioral changes and concomitant neuropathological events in icvSTZ rat model of sporadic Alzheimer diseases (AD). In the present study, we aimed to explore the effect of Ago (40 mg/kg, i.p. for 30 days) on beta-amyloid (Aβ) metabolism in icvAβ rat model of AD. The melatonin analogue was administered either simultaneously with Aβ (AβAgo1) or 30 days later during the late stage of the progression of AD (AβAgo2). Treatment with Ago in the early stage of AD attenuated anxiety and depressive-like responses but was inefficient against Aβ-induced impairment of hippocampus-dependent spatial memory. The melatonin analogue, administered both during the early and the late stage of AD, corrected to control level the elevated Aβ in the frontal cortex (FC) and the hippocampus. The concentration of α-secretase was enhanced by AβAgo1 compared to the sham- and Aβ-veh groups in the hippocampus. No changes in the concentration of β-secretase in the FC and the hippocampus as well as of γ-secretase in the FC were observed among groups. Both the AβAgo1 and AβAgo2 attenuated to control level the Aβ-induced increased concentration of γ-secretase in the hippocampus. AβAgo1 exerted also structure-specific neuroprotection observed mainly in the CA1, septal CA3b subfield of the dorsal hippocampus and septo-temporal piriform cortex (Pir) and partially in the temporal CA3c, septal and temporal Pir. These findings suggest that Ago treatment in the early stage of AD can exert beneficial effects on concomitant behavioral impairments and neuroprotection in associated brain structures. The antidepressant administration both in the early stage and after the progression of AD affected Aβ metabolism via decreasing of γ-secretase concentration in the hippocampus.