The effect of three compounds known to allosterically modulate binding to the GABA/benzodiazepine/picrotoxin receptor complex on 4-hydroxy-2,3 [3H]butyric acid (GHB) binding was investigated. Pentobarbital, pentylenetetrazole, and picrotoxin enhanced [3H]GHB binding in a dose dependent fashion. Pentobarbital enhanced 4-hydroxy-2,3 [3H]butyric acid binding was associated with an increase in Bmax while pentylenetetrazole and picrotoxin altered the affinity of GHB for its binding site producing a decrease in Kd. These findings suggest that the GHB and GABA receptor complex may share certain moieties in common.