OXYTOCIN AND VASOPRESSIN MESSENGER-RNA EXPRESSION IN RAT HYPOTHALAMUSFOLLOWING KAINIC ACID-INDUCED SEIZURES

In this study, the regulation of hypothalamic oxytocin and vasopressin messenger RNA expression following the induction of seizures was inve stigated by in situ hybridization. Following kainic acid-induced seizu res, a significant increase in oxytocin messenger RNA in the paraventr icular nucleus was demonstrated at 1.5 h, one and two weeks; its level decreased at three weeks and was significantly increased again at fou r weeks; at eight weeks the messenger RNA level still remained higher than that of controls. Vasopressin messenger RNA in the paraventricula r nucleus was increased significantly only at 1.5 h following inductio n of seizures. The oxytocin messenger RNA level in the supraoptic nucl eus was also increased early at 1.5 h and later at four weeks followin g seizures; however, these increases did not last as long as those in the paraventricular nucleus. Vasopressin messenger RNA in the supraopt ic nucleus was also increased after the initial seizures; however, its messenger RNA level vacillated up and down throughout the post-seizur e times studied. The earliest significant increase of vasopressin mess enger RNA was at one week after seizures, and there was a late signifi cant increase of vasopressin messenger RNA at three weeks after seizur es. The present study demonstrates that following kainic acid-induced seizures both, the oxytocin and vasopressin messenger RNA expressions, were up-regulated and these up-regulations were long-term events. The increase of oxytocin messenger RNA in the paraventricular nucleus was more persistent than the others. The pattern of messenger RNA up-regu lation was different for oxytocin and vasopressin, and different in th e paraventricular nucleus and supraoptic nucleus. These different patt erns of messenger RNA elevations suggest that the different components of the rat hypothalamus were regulated differentially by kainic acid- induced seizures.