Lentiviral expression of HINT1 increases cell viability in the presence of NMDA. (A) Fluorescence photomicrograph of HINT1-/- cortical cell cultures uninfected or infected with lentiviral particles. The cells were immunolabelled with anti-HINT1 Ab (green). The nuclei were counterstained with 4,6-diamidino-2-phenylindole. Inset: Immunodetection of HINT1. (B) The cultures were infected and exposed to 30 μM of NMDA for 24 h. Cell death was measured by LDH efflux into the medium. The data shown represent the mean ± S.E.M. from 20 wells per experimental group. * Indicates a significant difference between HINT1-/- cortical cell cultures, p < 0.05, compared to those derived from WT mice. Φ Significant increase in cell viability of HINT1-/- cortical cell cultures infected with increasing amounts of the viral HINT1 vector compared to the HINT1-/- control group, p < 0.05.