Figure 3. Decreasing p-eIF2α makes adult mice more susceptible to cocaine-induced LTP and behavior.
(a–b) A low dose of cocaine (5 mg/kg) induced both LTP in VTA DA neurons (a, p<0.05, n=5, t8=4.193) and CPP in adult Eif2s1S/A mice (b, p<0.01, n=7, t12=3.411) compared to Eif2s1S/S mice (a, p=0.89, n=5, t8=0.14; b, p=0.2170, n=7, t12=1.303). (c–d) A low dose of cocaine (5 mg/kg) elicited LTP (c, p<0.001, n=6, t10=3.43) and CPP (d, p=0.1761, n=8 vehicle+cocaine, t14=1.425; p<0.0001, n=16 ISRIB+cocaine, t30=2.433) in ISRIB-injected adult mice compared to vehicle-injected mice. (e–f) DHPG (100 μM, 5 min) induced LTD in WT adult VTA DA neurons (e, p<0.001, n=5, t8=20.3) and vehicle-injected WT adult mice (f, p<0.001, n=5, t8=5.17), but not in Eif2s1S/A mice (e, p=0.26, n=7, t12=1.2) and ISRIB-injected mice (f, p=0.42, n=4, t6=0.86).
Figure 3—figure supplement 1. eIF2α phosphorylation is reduced in VTA from adult Eif2s1S/A mice. .
Western blots (top) show reduction in p-eIF2α in Eif2s1S/A mutant mice compared to wild-type littermates (Eif2s1S/S). Quantification of eIF2α phosphorylation vs. total-eIF2α is shown below (p<0.01, n=3 per group, t4=6.67).
Figure 3—figure supplement 2. Decreasing p-eIF2α makes VTA slices from adult mice more susceptible to cocaine-induced LTP in vitro. .
Direct application of a low concentration of cocaine (1 μM) increased AMPAR/NMDAR ratio 3–5 hr post-treatment in VTA DA neurons of Eif2s1S/A mice, as compared to wild-type controls (n=5-11 per group, F1,32=6.56, p<0.01 Eif2s1S/A vs. wild-type control).
Figure 3—figure supplement 3. In adult mice, systemic administration of ISRIB alone failed to induce LTP in VTA DA neurons and CPP.
a, b. i.p. injection of ISRIB (2.5 mg/kg) alone did not induce LTP (a, p=0.79, n=6/3 ISRIB/vehicle, t7=0.28) or CPP (b, p=0.329, n=9, t16=1.008), as indicated by the lack of potentiation of VTA DA neurons and difference between average pre- and post-test preference scores, respectively.