Figure 4. tPA-induced early preconditioning.

(A) Mean cell survival in hippocampal neurons treated with either tPA (in nM) or with itPA followed by exposure to OGD conditions during 55 minutes. n = 20 for each observation. Error bars denote SD. *P < 0.05 compared with untreated cells; **P < 0.05 compared with untreated neurons and with cells treated with 500 nM tPA. (B and C) Mean hippocampal neuronal survival following exposure to OGD conditions (55 minutes) and incubation with 1 μM tPA alone or in combination with either α₂-antiplasmin (AP, 140 nM) or RAP (100 nM) or with either one of the NMDAR antagonists MK-801 (10 μM) or DL-AP5 (50 μM) or with plasmin alone (Pl; 100 nM) or with RAP alone. n = 20 in B and n = 15 in C. Error bars denote SD. In B: *P < 0.05 compared with cells left untreated; **P < 0.05 compared with cells kept under OGD conditions; ***P < 0.05 compared with neurons maintained under OGD conditions and with tPA alone. In C: *P < 0.05 compared with cells maintained under OGD conditions and either left untreated or incubated with MK-801 or DL-AP5 alone. (D) Mean neuronal survival following incubation with 250 μM KA either alone or in combination with 1 μM tPA. *P < 0.05 compared with untreated cells. n = 10. Error bars denote SD in all panels. “PREC.” (preconditioning) indicates the moment when cells were incubated with each compound.