SPONTANEOUS RECURRENT SEIZURES IN RATS - AMINO-ACID AND MONOAMINE DETERMINATION IN THE HIPPOCAMPUS

Rats subjected to structural brain damage induced by sustained convuls ions triggered by systemic administration of pilocarpine (PILO) are a useful model for investigation of the mechanisms essential for seizure generation and spread in rodents. After PILO administration, three di stinct phases are observed: (a) an acute period of 1-2 days' duration corresponding to a pattern of repetitive limbic seizures and status ep ilepticus; (b) a seizure-free (silent) period characterized by a progr essive return to normal EEG and behavior of 4-44 days' duration; and ( c) a period of spontaneous recurrent seizures (SRS) starting 5-45 days after PILO administration and lasting throughout the animal's life. P ILO (320-350 mg/kg intraperitoneally, i.p.) was administered to rats, and the content of hippocampal monoamines and amino acids was measured in the acute, silent, and SRS periods by liquid chromatography. Norep inephrine (NE) level was decreased during all periods whereas dopamine (DA) content was increased. Serotonin (5-hydroxytryptamine, 5-HT) was increased only in the acute period. Utilization rate measurement of m onoamines showed increased NE consumption and decreased DA consumption during all phases. 5-HT utilization rate was increased only in the ac ute period. Amino acid content showed a decrease in aspartate (ASP) an d glutamate (GLU) concentrations associated with increased gamma-amino butyric acid (GABA) level during the acute period. The silent phase wa s char acterized by a decrease in glycine (GLY) and GABA levels and an increase in GLU concentration. The SRS period showed an increase in a ll amino acid concentrations. These findings show important neurochemi cal changes in the course of establishment of an epileptic focus after brain damage induced by status epilepticus triggered by pilocarpine.