NCS-382 possesses antagonistic properties at gamma-hydroxybutyrate receptor sites. Its effect on the sedative/cataleptic behaviour observed in rats after gamma-hydroxybutyrate administration was investigated. NCS-382 diminished, in a dose-dependent manner, the sedative and/or cataleptic effects of gamma-hydroxybutyrate, as revealed by a variety of sensorimotor tests. These results indicate that the well-known sedative/anaesthetic effects induced by gamma-hydroxybutyrate administration are provoked via stimulation of a specific class(es) of gamma-hydroxybutyrate receptors which exist in the rat brain and which could mediate a local stimulation of opiate synthesis and release.