A. Effect of various concentrations of the D1-receptor antagonist SCH 23390 on cell survival after two-hour incubation. No effect was observed on PC-12 cells maintained under normal conditions or in xenon, however, for cells kept in nitrogen, a concentration-dependent decrease of cellular damage was found, indicating that the D1-receptor was involved to convey the cellular damage. (n = 4; **P < 0.01 and *P < 0.05 with respect to untreated controls). B. Effect of various concentrations of the D2-receptor antagonist sulpiride on cell survival after two-hour incubation. No protective effect of sulpiride was found for cells incubated in nitrogen, even a slight increase of cellular damage was seen with increasing concentrations of sulpiride.