Immunoreactivity to excitatory aminoacid (EAA) receptors in the nucleus tractus solitarius (NTS) of rats submitted to chronic intermittent hypoxia (CIH)

Abstract

CIH in rats produces important changes in the central neural control of the cardiovascular and respiratory functions. In the present study we evaluated possible changes in the EAA receptors in the NTS of rats after CIH. To this purpose, the rats were submitted to CIH (FiO2 of 6% for 40 s, every 9 min, 8 h/day) during 35 days (CIH rats, n=8) and a significant increase in the mean arterial pressure (113 ± 3 vs 102 ± 2 mmHg) and in the heart rate (395 ± 11 vs 364 ± 7 bpm) were observed in comparison to control rats (n=5) maintained under normoxia (FiO2 of 20.8%). We analyzed different subunits of AMPA and NMDA receptors in the NTS of control and CIH rats by immunofluorescence using rabbit polyclonal antibodies (Chemicon) anti different subunits of AMPA (GLUR1, GLUR2/3, GLUR4) or NMDA (NMDAR1) receptors. Goat anti rabbit IgG conjugated to Cy3 (Jackson Immunoresearch) was used as secondary antibody. The intermediate and caudal commissural subnucleus of the NTS were analyzed and the data show a clear decrease in the fluorescence labeling of NMDAR1 subunit mainly in the caudal NTS of CIH rats in comparison to control rats. The NMDAR1, GLUR1 and GLUR2/3 subunits presented a stronger immunoreactivity than GLUR4 in the NTS of both control and CIH animals. The decrease in NMDAR1 subunit immunoreactivity in the NTS of CIH rats may be associated with the changes in the cardiovascular function observed in rats submitted to CIH. Supported by FAPESP and CNPq.