Acute effects of N-(2-propylpentanoyl)urea on hippocampal amino acid neurotransmitters in pilocarpine-induced seizure in rats.

The present study aimed to investigate the anticonvulsant activity as well as the effects on the level of hippocampal amino acid neurotransmitters (glutamate, aspartate, glycine and GABA) of N-(2-propylpentanoyl)urea (VPU) in comparison to its parent compound, valproic acid (VPA). VPU was more potent than VPA, exhibiting the median effective dose (ED(50)) of 49 mg/kg in protecting rats against pilocarpine-induced seizure whereas the corresponding value for VPA was 322 mg/kg. In vivo microdialysis demonstrated that an intraperitoneal administration of pilocarpine induced a pronounced increment of hippocampal glutamate and aspartate whereas no significant change was observed on the level of glycine and GABA. Pretreatment with either VPU (50 and 100 mg/kg) or VPA (300 and 600 mg/kg) completely abolished pilocarpine-evoked increases in extracellular glutamate and aspartate. In addition, a statistically significant reduction was also observed on the level of GABA and glycine but less than a drastic reduction of glutamate and aspartate level. Based on the finding that VPU and VPA could protect the animals against pilocarpine-induced seizure it is suggested that the reduction of inhibitory amino acid neurotransmitters was comparatively minor and offset by a pronounced reduction of glutamate and aspartate. Therefore, like VPA, the finding that VPU could drastically reduce pilocarpine-induced increases in glutamate and aspartate should account, at least partly, for its anticonvulsant activity observed in pilocarpine-induced seizure in experimental animals. Some other mechanism than those being reported herein should be further investigated.