, 2000). In our current experiment, there were no differences in the hippocampal levels of GAP-43 between the SC and SSD rats. These data are consistent with those found by Gao et al. (2010), where the GAP-43 expression INK 128 clinical trial did not change after daily total SD (12 h for 3 days). In contrast, we observed an increase in the hippocampal levels of GAP-43 in exercised rats even after 5 days of exercise cessation. Although we did not find differences in IA performance between the Ex and SC groups, the increased expression

of GAP-43 may have mediated, at least in part, the prevention of memory loss in the ExSD group. Synapsin I is a nerve terminal-specific synaptic vesicle associated phosphoprotein that is involved CX-5461 molecular weight in both the synaptogenesis and the plasticity of mature synapses by controlling synaptic vesicle trafficking at pre- and post-docking levels (Evergren et al., 2007). Previous studies showed an increase in synapsin I immunoreactivity during LTP (Sato et al., 2000) and revealed that 6 days of spatial learning in the MWM increased

synapsin I mRNA and protein expression (Gomez-Pinilla et al., 2001). The hippocampal levels of synapsin I did not change in any of the experimental conditions in the present study. Guzman-Marin et al. (2006) observed a reduction in synapsin I mRNA expression in the hippocampus after 8 and 48 h of SD. In contrast, a recent study demonstrated that 96 h of paradoxical SD increased the levels of total synapsin I and its phosphorylated form in the synaptosomes from the whole brain of rats (Singh et al., 2012). These discrepancies may be due the different periods and methods of SD used in the two studies as well as in the method for analyzing synapsin I. The expression of NADPH-cytochrome-c2 reductase synapsin I is modulated differently depending on the type and volume of exercise (Cassilhas et al., 2012a, Ferreira et al., 2011 and Vaynman et al., 2004). A recent study conducted in our laboratory demonstrated that, independent of the type of exercise (aerobic or resistance), 8 weeks of exercise was able to increase the levels of synapsin I in the rat hippocampus (Cassilhas

et al., 2012a). Moreover, studies have shown an increase in hippocampal levels of this protein after just 3 (Vaynman et al., 2004) or 7 (Ferreira et al., 2011) days of aerobic exercise. In the present study, the absence of changes in synapsin I expression after 20 days of exercise is in accordance with previous studies (Ferreira et al., 2011 and Molteni et al., 2002) where no significant differences were found after longer periods (28 and 15 days) of exercise. Synaptophysin, a major integral glycoprotein attached to the membrane of synaptic vesicles, was not affected by SD or by exercise (Tarsa and Goda, 2002). Synaptophysin acts as an important protein in the biogenesis of synaptic vesicles (Thiele et al.