Metaldehyde, when administered orally to mice at a dose of 1 g kg‐1, produced convulsions and death within 2 h. Brain concentrations of noradrenaline (NA) 5‐hydroxytryptamine (5‐HT) and 5‐hydroxyindoleacetic acid (5‐HIAA) were significantly reduced in these animals relative to controls. Treatment with either intraperitoneal clonidine or diazepam 20 min after administration of metaldehyde reduced the mortality rate and in mice surviving for 5 h, the decrease in brain NA and 5‐HT concentrations were significan