Effect of Short and Long-Term Treatment with Omega-3 Fatty Acids on Scopolamine-Induced Amnesia

   Two omega-3 fatty acids including docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are essential for the physiologic function of neuronal cell membrane. Normal function of neuronal cell membrane requires appropriate composition of fatty in its structure. Present study was designed to compare the effect of short-term and long-term pretreatment with omega-3 fatty acids on scopolamine-induced amnesia and possible involvement of apoptotic or oxidative pathways. Male Wistar rats were gavaged by omega-3 fatty acids [60 mg/Kg (DHA + EPA)] or saline for 2 weeks (short-term model) or 8 weeks (Long-term model), then received intra-CA1 scopolamine (2 µg/rat). Finally, the avoidance response was examined and hippocampus tissue was prepared. Intra-CA1 injection of scopolamine abolished the memory performance in rats. Short-term or long-term pretreatment with omega-3 fatty acids improved memory (p < 0.01 and p < 0.001, respectively). Pretreatment for 2 weeks had no effect on the tissue Malondialdehyde (MDA) contents or SOD and CAT activity. In addition, pretreatment for 2 weeks with omega-3 fatty acids had no effects on tissue Bax and Bcl-2 expression. Conversely, long-term pretreatment with omega-3 fatty acids decreased tissue MDA contents (p < 0.01), SOD activity (p < 0.05) and increased CAT activity (p < 0.01). Long-term pretreatment with omega-3 fatty acids also decreased Bax protein expression (p < 0.05) with no effect on the expression of Bcl-2 protein. In conclusion, long-term exposure to omega-3 fatty acids inhibited the scopolamine-induced oxidative stress, apoptosis and amnesia while the effect of short-term treatment was restricted to the improved memory without significant effect on apoptosis or oxidative stress. Therefore, long-term treatment with low doses of omega-3 fatty acids suggested a suitable treatment for amnesia.