Increased enkephalin and dynorphin immunoreactivity in the hippocampus of seizure sensitive Mongolian gerbils

Radioimmunochemistry (RIA) and immunocytochemistry (ICC) were used to measure proenkephalin and prodynorphin peptides in the brain of a genetic model of epilepsy, the seizure-sensitive (SS) Mongolian gerbil. Brain levels of both [Met5]- or [Leu5]-enkephalin (ME-LI) and dynorphin A1-8 and dynorphin A1-17 (DN-LI) like immunoreactivity were increased in the hippocampal region of the SS gerbil. However, ME-LI and DN-LI did not follow the same patterns. ME-LI was significantly increased in the SS gerbils (post-seizure) compared to SR gerbils while ME-LI in SS (preseizure) gerbils was not significantly different from SR gerbils. DN-LI was significantly increased in the hippocampal region of both SS (preseizure) and SS (postseizure) gerbils compared to SR gerbils. These results strongly imply differences in the regulation of proenkephalin and prodynorphin metabolism in the Mongolian gerbil. The differences in metabolic regulation may signal fundamentally different roles of these opioid peptides in the modulation of seizure activity in this animal.