NON-NMDA AND NMDA RECEPTORS TRANSMIT AREA POSTREMA INPUT TO AORTIC BARORECEPTOR NEURONS IN NTS

We sought to determine whether glutamate acting at both N-methyl-D-asp artate (NMDA) and non-NMDA receptors transmits area postrema (AP) exci tatory inputs to nucleus tractus solitarii (NTS) neurons in the aortic baroreceptor or vagal afferent pathways in vivo. In alpha-chloralose- anesthetized rabbits, we recorded extracellular NTS neuronal responses to low-frequency aortic depressor nerve (ADN), vagus nerve, and AP st imulation and to iontophoresis of lpha-amino-3-hydroxy-5-methylisoxazo le-4-propionic acid and NMDA during control, iontophoresis of ,3-dihdr oxy-6-nitro-7-sulfamoylbenzo(f)quinoxaline (NBQX), DL-2-amino-5-phosph onovaleric acid (AP5), or both, and recovery conditions. In neurons re ceiving AP and ADN inputs, NBQX attenuated AP- and ADN-evoked response s by 46 (P = 0.0206) and 49% (P = 0.0042). AP5 attenuated AP- and ADN- evoked responses by 39 (P = 0.0270) and 40% (P = 0.0157). NBQX + AP5 a ttenuated AP- and ADN-evoked responses by 74 (P = 0.0040) and 75% (P = 0.0028). In neurons receiving AP and vagal inputs, AP transmission wa s attenuated by 58, 60, and 98%; vagal transmission was attenuated by 62, 35, and 83% during NBQX, AP5, and both antagonists, respectively. These data suggest that both non-NMDA and NMDA receptors transmit AP i nput to NTS neurons in aortic baroreceptor or vagal afferent pathways.