Upregulation of arginine vasopressin synthesis in the rat hypothalamus after kainic acid-induced seizures.

We examined the effects of kainic acid (KA)-induced seizures on arginine vasopressin (AVP) gene expression in the paraventricular (PVN) and the supraoptic nuclei (SON) of normal rats using in situ hybridization histochemistry. We also investigated the expression of the AVP-enhanced green fluorescent protein (eGFP) fusion gene after KA-induced seizures in transgenic rats. AVP heteronuclear (hn) RNA levels in the PVN and the SON were significantly increased at 3h and 24h after subcutaneous (s.c.) administration of KA in normal rats. AVP mRNA levels in the PVN and the SON did not change significantly at 3h, 24h and 1 week after s.c. administration of KA in normal rats. In KA-administered transgenic rats, AVP-eGFP fluorescence in the magnocellular and parvocellular divisions of the PVN and the SON were significantly stronger compared to vehicle-administered transgenic rats. By pretreatment with MK-801 (nonselective N-methyl-D-aspartate, NMDA, receptor antagonist), AVP-eGFP transgenic rats after administration of KA did not show preconvulsive symptoms or convulsions and AVP-eGFP fluorescence in the magnocellular and parvocellular divisions of the PVN and the SON of these rats was significantly reduced. These results suggested that KA-induced increases in AVP transcripts and AVP were prevented by MK801 because seizure activity was prevented or reduced.