- The postictal immobility syndrome was examined in five experimental grand mal epilepsy models in an attempt to analyze separately the behavioral and underlying neurochemical aspects of the rigid-catatonic and flaccid-cataleptic states. Catalepsy and analgesia were found in varying degrees after maximal electroshock (MES), metrazol, picrotoxin, and Ro 5–3663 activated seizures. Signs of rigidity were noticed after the MES and picrotoxin seizures. Kindled seizures were followed by explosive behavior without signs of rigidity, catalepsy, and analgesia. Naloxone reduced the duration but not the score (intensity) of catalepsy and failed to selectively antagonize analgesia. The relative representation of the tonic stage of convulsions seemed to be the major determinant of the development of catatonic-cataleptic symptomatology. It is suggested that more than a single neurotransmitter system is involved in the postictal immobility syndrome and each epilepsy model has its unique neurochemical profile.