IMMUNO-LOCALIZATION OF KYNURENINE AMINOTRANSFERASE (KAT) IN THE RAT MEDULLA AND SPINAL-CORD

IN the mammalian brain, kynurenine aminotransferase (KAT) is pivotal t o the synthesis of kynurenic acid, a preferential antagonist at the st rychnine-insensitive NMDA-glycine site. As NMDA receptors are involved in autonomic function, we have examined the immunohistochemical local ization of KAT in the medulla and spinal cord of the rat. KAT immunore activity (KAT-li) was found throughout these areas, in both glia and n eurons. Unlike the mainly astrocytic localization in forebrain structu res, KAT-li was predominantly neuronal, notably in areas important for Blood pressure and heart rate regulation: ventral medulla, nucleus am biguus, nucleus of the solitary tract and intramediolateral cell colum n of the spinal cord. The presence of KAT in these nuclei supports a n euromodulatory role for kynurenic acid in NMDA-mediated autonomic func tion.