Hypoxia induces c-Fos protein expression in NMDA but not AMPA glutamate receptor labeled neurons within the nucleus tractus solitarii of the conscious rat

Glutamatergic transmission within the nucleus tractus solitarii (nTS) is cr itical to full expression of hypoxia-induced cardiorespiratory responses in the rat. To further examine the role of N-methyl-d-aspartate (NMDA) and al pha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) glutamate recepto rs in these responses, double-labeling studies of immunoreactivity for c-Fo s protein and either NMDA (NR1) or AMPA (mGluR2/3) receptor expression were conducted in normoxic rats and in hypoxic rats receiving vehicle, MK801, o r NBQX. Hypoxia markedly increased c-Fos immunoreactivity within nTS neuron s which in the vast majority co-labeled for NMDA. Furthermore, MK801 marked ly attenuated such responses. In contrast, co-localization of AMPA and c-Fo s occurred in only a small proportion of neurons, and NBQX failed to modify hypoxia-induced c-Fos enhancements. These data suggest a predominant role for NMDA but not for AMPA glutamate receptors in nTS mediated components of the hypoxic response. (C) 1999 Elsevier Science Ireland Ltd. All rights re served.