Fig. 4. (A ) Addition of glycine (10 μm) to Ultiva®(white bars ; 24 nm remifentanil plus 0.4 μm glycine) does not induce an additive effect on either receptor subtype combination compared with Ultiva®(black bars ; 24 nm remifentanil plus 0.4 μm glycine alone) (P > 0.05; n = 10; vertical bars ± SEMs). (B ) Preapplication of a saturating glycine concentration (10 mm; white bar ) before application of Ultiva®(remifentanil 0.24 nm plus glycine 4 nm) does not enhance Ultiva®-induced currents in N -methyl-d-aspartate receptors (NR1A/2A) (n = 10; vertical bars ± SEMs). (C ) Glutamate/glycine-evoked N -methyl-d-aspartate receptor responses (NR1A/2A) are inhibited by the glycine site antagonist 7-CK (5 μm; white bars ) in a glycine concentration–dependent manner. Responses to both Ultiva®concentrations (remifentanil 0.1 mm plus glycine 3.1 mm and remifentanil 0.25 nm plus glycine 4 nm) are not affected by 7-CK (*P < 0.05; n = 10; vertical bars ± SEMs).