Fig. 4. Effects of propofol on  N -methyl-d-aspartate (NMDA) receptor NR1 serine phosphorylation and NMDA receptor–mediated Ca²⁺increases in cultured rat hippocampal neurons. (  A and  B ) Propofol reduced cellular levels of pNR1-Ser897 and pNR1-Ser896 without a change in NR1 levels (mean ± SEM, n = 4–6). Propofol was incubated at 1, 10, or 50 μm for 5 min. (  C ) Effects of bicuculline (Bicucu) on propofol-induced reduction of NR1 phosphorylation (mean ± SEM, n = 4). Bicuculline (20 μm) was added 30 min before and during a 5-min incubation with propofol. Note that propofol indistinguishably reduced phospho-NR1 proteins in the absence or presence of bicuculline. (  D ) Changes in [Ca²⁺]ⁱlevels in cultured hippocampal neurons after bath application of NMDA in the presence of propofol or vehicle (Veh). The [Ca²⁺]ⁱlevels were measured by somatic fura-2 ratio fluorescence. Propofol (10 μm) was incubated 5 min before addition of NMDA (100 μm, 20 s). The values are expressed as mean ± SEM measured from 15–21 neurons. *  P < 0.05  versus basal levels.