Correlation between electrocorticographic and motor phenomena induced by pentamethylenetetrazol during ontogenesis in rats.

Motor and electrocorticographic (ECoG) phenomena induced by pentamethylenetetrazol (PTZ) were directly compared in adult as well as in young rats (age groups of 7, 12, and 18 days). The technique for implantation of cortical electrodes was elaborated in young rats. Myoclonic jerks were elicited by PTZ in all age groups studied. In adult animals they were accompanied by isolated spikes and/or spike-and-wave complexes, whereas in 7-day-old rats there was a poor correlation between ECoG abnormalities and myoclonic jerks. With increasing age an improved correlation between ECoG abnormalities and behavioral changes were noted. After further injections of PTZ, rats had generalized tonic-clonic motor seizures. Ictal ECoG activity usually started in one cortical region in 7-day-old rats and became progressively generalized whereas in older rats generalized electrical discharges accompanied the motor seizures from onset. The clonic phase of motor seizures was not always accompanied by specific ECoG changes in young rats. At all ages the correlation between ECoG activity and individual phases of the generalized tonic-clonic seizures was poor.