The influence of excitatory blockade elicited by uncompetitive N-methyl-D-aspartate (NMDA)/glutamate receptor antagonists on inhibitory GABAergic systems is not well understood. Adult male rats were injected i.p. with a single dose of the prototypical uncompetitive antagonist MK-801 (0.2-10 mg/kg) and in situ hybridization was performed to measure mRNA levels of γ-aminobutyric acid type A (GABA) receptor subunits (α1-6, β1-3, γ1-3, δ, ε, and θ). A significant decrease in δ subunit mRNA levels, that reached ∼70% of saline-treated values, was observed in the hippocampal dentate gyrus following MK-801 administration. Other subunits did not display statistically significant alterations. These data demonstrate selective actions on GABA receptor subunit levels that result from blockade of excitation by MK-801. © 2004 Elsevier Ireland Ltd. All rights reserved.