Extended Data Fig. 8: STD LTP requires presynaptic activity and depends on NMDA, Group I mGluR and astrocyte calcium mobilization.
(a) Top. Representative traces before (1) and after (2) repetitive postsynaptic AP without presynaptic spike. Bottom. Time course of the EPSC before and after repetitive postsynaptic AP without presynaptic spike. Scale bars 50 pA, 20 ms. (b) Bargraph of the EPSC before (basal) and after (post-AP) repetitive postsynaptic AP (n = 6/3, p = 0.9). Scale bars 10 mV, 50 ms. (c) Representative EPSCs 30 minutes after STDP protocol in control condition (black trace), in the presence of D-AP5 (light gray trace) and in the presence of MPEP + LY (dark gray trace). Scale bars 40 pA, 20 ms. (d) Time course of the LTP induced by STDP in control condition (n = 8 cells, p < 0.001; black circles; control), under NMDAR antagonist, D-AP5 (50 µM; n = 6, p = 0.94; light grey circles; D-AP5), and in the presence of group I mGluR antagonists, MPEP and LY (50 µM + 100 µM; n = 5, p = 0.48; dark grey circles; MPEP + LY). (e) Bargraph of the LTP induced by STDP in control condition (black graph; control), under NMDAR antagonist, D-AP5 (light grey graph; D- AP5) and in the presence of group I mGluR antagonists, MPEP and LY (dark grey graph; MPEP + LY). Note that LTP is abolished in the presence of D-AP5 (p < 0.05) and MPEP + LY (p < 0.05), demonstrating that LTP depends on NMDAR and Group I mGluRs. (f) Representative EPSCs 30 minutes after STDP protocol in control condition (black trace), in the presence of D-AP5 (light gray trace) and in the presence of MPEP + LY (dark gray trace). Scale bars 40 pA, 20 ms. (g) Time course of the LTP induced by STDP in control condition (black circles; control), in calcium chelator BAPTA loading astrocytes (20 mM; n = 6, p = 0.95; white circles; aBAPTA), and in IP3R2−/− (n = 6, p = 0.40; red circles; IP3R2−/−). (h) Bargraph of the LTP induced by STDP in control condition (black circles; control), in calcium chelator BAPTA loading astrocytes (white circles; aBAPTA), and in IP3R2−/− (red circles; IP3R2−/−). Note that LTP is prevented in BAPTA (p < 0.01) loading astrocyte network and in IP3R2−/− (p < 0.05), demonstrating the necessary role of astrocytes activation LTP induction. Adult animals ( ≥ 6 weeks; males and females) were used; One-way ANOVA, post hoc Dunn. *p < 0.05, **p < 0.01, **p < 0.001; Student’s paired t-test. #p < 0.01, ##p < 0.01, ###p < 0.001; one-way ANOVA with post hoc Dunn’s; n.s., nonsignificant (p > 0.05). Data are mean ± s.e.m.
