SEIZURES INDUCED BY HOMOCYSTEINE IN RATS DURING ONTOGENY

We studied the convulsant action of homocysteine in 211 immature and a dult Wistar albino rats. Homocysteine elicited minimal, predominantly clonic, and major generalized tonic-clonic seizures at six different d evelopmental stages, from 7 days to adulthood. Nevertheless, some age- dependent differences in the seizure pattern were apparent. Minimal se izures in immature rats lasted less than or equal to 20 min, thus repr esenting an epileptic status, whereas in adult animals these seizures mere much shorter, lasting only less than or equal to 40 s. In additio n, flexion seizures were observed in 7- and 12-day-old rats, only rare ly in 15-and 18-day-old animals, and never in the 25-day-old and adult rats. ECoG recordings demonstrated a nearly isoelectric pattern durin g homocysteine-induced seizures in 7- and 12-day-old rat pups. In olde r rats, spikes or sharp waves were recorded, but precise electroclinic al correlations were poor. The greater sensitivity of younger animals to kainic acid (KA) and N-methyl-D-aspartate (NMDA), as reported previ ously, was not evident in the case of homocysteine-induced seizures. T his observation, together with a different behavioral pattern, suggest s that homocysteine cannot be considered a simple agonist of the kaina te or NMDA type of excitatory amino acid receptors. The exact mechanis m of the convulsant action of homocysteine, both Juring development an d in adulthood, remains to be clarified.