AIM: To study the roles of N-methyl-D-aspartate (NMDA) receptors in arteria
l baroreflex. METHODS: Experiments were performed in 17 urethane-anaestheti
zed male Sprague-Dawly rats. Twenty-seven rostral ventrolateral medulla (RV
LM) neurons were electrophysiologically identified as putative presympathet
ic neurons. Responses of these neurons to baroreflex activation were used a
s an index to observe the effects of 3-(2-carboxypiperazin-4-yl) propyl-l-p
hosphonic acid (CPP) microinjected (0.1 mu L, 50 mmol . L-1) into the nucle
us tractus solitarii (NTS) or the caudal ventrolateral medulla (NLM) ipsila
terally. RESULTS: In the NTS, CPP eliminated or attenuated the inhibition o
f these neurons induced by aortic nerve stimulation, but the inhibition ind
uced by elevation of arterial pressure was not eliminated and the cardiac c
ycle-related rhythm of spontaneous discharge still existed. Whereas in the
CVLM, CPP eliminated not only the inhibition of these neurons induced by ao
rtic nerve stimulation, but the inhibition induced by blood pressure elevat
ion and the cardiac cycle-related rhythm of spontaneous discharge disappear
ed. CONCLUSION: NMDA mechanism is importantly involved in the mechanism of
baroreflex both in the NTS and in the CVLM; the barosensitive neurons in th
e NTS project to ipsilateral CVLM.