Figure 2. Acute traumatic stress in combination with re-exposure stress leads to a long-lasting decrease of hippocampal synapsin Ia-b/IIa expression.

(A) Course of experiment: C57BL/6 NCrl mice (batch PTSD I and II, see Table 2) were subjected to a single electric footshock, (“shock”) or mock treatment (“no shock”). Different groups of them were sacrificed at different time-points after footshock application. Three brain regions were dissected and tissues were lysed and subjected to western blot analysis (WB) for determination of synapsin expression levels. On day 28 after exposure to footshock or mock treatment, mice were subjected to behavioral tests (which included re-exposure to the trauma context) and sacrificed on day 60, while mice sacrificed on day 2 or day 28 were not subjected to behavioral analyses. For assessment of PTSD-like symptoms, the acoustic startle response, the generalized fear response (both in a neutral context and in an experimental context similar to the shock context) and the conditioned fear response were assessed as described in the methods section and in Figure 1. Mice of batch PTSD II were additionally subjected to a CODA test on day 42 (described in the methods section and in Figure S2). Figure S1 provides further details of behavioral protocols. (B–D) Representative immunoblots show expression levels of synapsin Ia-b/IIa and, for control, glycerinaldehyd-3-phosphat-dehydrogenase (GAPDH) of footshocked (“shock”) or control (“no shock”) mice, respectively. Grouped graphical inserts belong to one and the same gel. Graphs show expression levels of synapsin Ia-b/IIa after normalization to GAPDH 2 days (B), 28 days (C), and 60 days (D) after shock in lysates of bilateral hippocampi (HC), prefrontal cortices (PFC), or cerebella (CER) of footshocked and control mice, respectively. Synapsin Ia–b/IIa expression levels of footshocked mice are presented as percent of those of control mice (set at 100%). Plotted data represent means ± SEM, n = 6 for d2 and d28, n = 12 (batches PTSD I and PTSD II) for d60. Statistical significance was calculated using students t-test and is indicated by t p<0.1, * p<0.05 and *** p<0.001 (d2: HC t (10) = 2.631, p = 0.025, PFC t (10) = 0.603, p = 0.560, CER t (10) = 0.398, p = 0.698; d28: HC t (10) = 1.963, p = 0.078, PFC t (10) = 1.279, p = 0.229, CER t (10) = 0.044, p = 0.965; d60: HC t (22) = 4.332, p<0.001, PFC t (22) = 1.408, p = 0.173, CER t (10) = 0.540, p = 0.601).