Amino acid and monoamine alterations in the cerebral cortex and hippocampus of mice submitted to ricinine-induced seizures

The alkaloid ricinine isolated from the plant Ricinus communis, when administered to mice at high doses, induces clonic seizures accompanied by electroencephalographic alterations in the cerebral cortex and hippocampus. The lethal nature of ricinine-induced seizures is considered to be a good model for the study of the events that cause death during clonic seizures, particularly those related to respiratory spasms. The initial signs (pre-seizure period) were marked by exophthalmus and decreased locomotor behavior. Animals killed during the preseizure period presented an increased utilization rate (HVA/DA) of dopamine (DA), an increased concentration of noradrenaline (NA), and a decreased concentration of glutamate (Glu), glutamine (Gln), taurine (Tau), and serotonin (5-HT) in the cerebral cortex. The seizure period is characterized by the occurrence of hind limb myoclonus and respiratory spasms, which are followed by death. Alterations in the cerebral cortex concentration of these neurotransmitters persisted during the seizure period. These alterations are only partially observed in the hippocampus, mainly during the seizure period. The present results suggest that an increased release of Glu in the cerebral cortex can be implicated in the genesis of the ricinine-induced seizure and that it triggers many anticonvulsive mechanisms, like the release of Tau, DA, 5-HT, and NA. (C) 2002 Elsevier Science Inc. All rights reserved.