Young-adult (n = 12) and P21 (n = 10) rats were exposed to a soman dose corresponding to 1.2 X LD50 (P21 rats: 74.4 μg/kg, young-adult rats: 132 μg/kg). A. Administration of HI-6 to P21 rats, at 20 min after soman injection, had no effect on seizures. B. Administration of 2.0 mg/kg ATS, at 20 min after soman injection, terminated seizures in the P21 rats, but not in the adult rats. ***p < 0.001 when seizure severity score is compared between P21 and adult rats at 40, 50, and 60 min after soman exposure (MANOVA, Bonferroni correction).