Suppressive Effects of Various Amino Acids against Ouabain-Induced Seizures in Rats

SUMMARY:The suppressive effect of various amino acids against ouabaininduced seizures was investigated in young female rats. The amino acids were injected into the left lateral ventricle 10 minutes prior to the intraventricular administration of 5 μg. of ouabain. Animals receiving 1.9 x 10-1M solutions of hypotaurine and of β- alanine were almost completely protected from the ouabain seizures. Administration of L-alanine and of glycine was also effective, although running and leaping seizures still occurred to some extent. Betaine reduced only clonic-tonic and whole body flexion and extension seizures. In contrast, L-proline exclusively suppressed clonic-tonic and focal clonic seizures. Rats injected with isethionic acid showed increases in incidence of running and leaping seizures while L-arginine in high concentrations caused aggravation in clonic-tonic seizures. L-cysteine, even in low concentrations, also brought about an increase in the occurrence and incidence of clonic-tonic seizures. The ED50of hypotaurine was 10.11 x 10-2M for running seizures and 4.63 x 10-2, M for clonictonic seizures; that of β -alanine was 14.01 x 10-2M for running seizures and 5.50 x 10-2M for clonic-tonic seizures. However, hypotaurine and β -alanine, the most effective compounds tested in the present studies, provided less protection than taurine previously examined by us under similar conditions (Izumi et al., 1973).