AMPA KAINATE RECEPTORS MEDIATE SYMPATHETIC CHEMORECEPTOR REFLEX IN THE ROSTRAL VENTROLATERAL MEDULLA/

Previous studies have reported that information from carotid chemorece ptors activates sympathetic premotor neurons in the rostral ventrolate ral medulla (RVLM) exclusively via N-methyl-D-aspartic acid (NMDA) rec eptors. In this study, we examined the possible involvement of lpha-am ino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate recept ors in the RVLM on sympathetic chemoreceptor reflex in pentobarbitone anaesthetised, vagotomised and artificially ventilated rats. Carotid c hemoreceptor stimulation with brief N-2 inhalation increased splanchni c sympathetic nerve activity and arterial pressure in animals that had received an intravenous injection of the non-competitive NMDA recepto r blocker, MK-801 (2 mg/kg), RVLM sympathetic premotor neurons could a lso be activated by brief hypoxia in the presence of MK-801. However, microinjection of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, a select ive AMPA/kainate receptor antagonist, 2 mM, 100 nl) into the RVLM afte r intravenous MK-801 abolished the hypoxia evoked sympathoexcitatory r esponse. These results demonstrate that AMPA/kainate receptors in the RVLM are involved in the chemoreceptor reflex pathway.