MOLECULAR AND IMMUNOCHEMICAL CHARACTERIZATION OF THE IONOTROPIC GLUTAMATE RECEPTORS IN THE RAT-HEART

Excitatory amino acids (EAA) and glutamate receptors (GluRs) play a fu ndamental role in the central nervous system (CNS). Ionotropic glutama te receptors (iGluRs) are coupled to ion channels, which are classifie d according to their most selective agonists, These ligand-gated chann els are permeable to Na+, K+, and Ca+. Interaction of EAA receptor is linked to Ca+2/Na+ influx. Influx changes lead to an action potential, which in the heart is transmitted along the cardiocyte membrane. Furt hermore, the heart has a rich innervation and specialized conduction s ystem for rapid conduction and regulation of cardiac rhythmicity, Avai lability of EAA receptors in the heart might be important for cardiac function. The following GluRs were cloned by isoform-specific RT-PCR f rom rat heart ribonucleic acid (RNA): GluR 1, GluR 3, GluR 4, GluR 7, Ka 1, and Ka 2. Expression in cardiac tissue was confirmed by western (for anti-GluR 2/3) and northern blots (for GluR 3, NMDAR 1, and Ka 2) . The anatomical distribution was investigated by immunohistochemistry , Antibodies to GluR 2/3, GluR 5/6/7, Ka 2, and NMDAR 1 showed the str ongest signals. These signals were specifically localized to cardiac n erve terminals, ganglia, conducting fibers, and some to myocardiocytes particularly in the atrium, Each antibody had a specific pattern of d istribution. This anatomical localization suggests that they might pla y a role in cardiac electrophysiology and pathology. (C) 1998 Elsevier Science Inc.