AIM: To study the roles of N-methyl-D-aspartate (NMDA) receptors in arterial baroreflex. METHODS: Experiments were performed in 17 urethane-anaesthetized male Sprague-Dawly rats. Twenty-seven rostral ventrolateral medulla (RVLM) neurons were electrophysiologically identified as putative presympathetic neurons. Responses of these neurons to baroreflex activation were used as an index to observe the effects of 3-(2-carboxypiperazin-4-yl) propyl-1-phosphonic acid (CPP) microinjected (0.1 microL, 50 mmol.L-1) into the nucleus tractus solitarii (NTS) or the caudal ventrolateral medulla (CVLM) ipsilaterally. RESULTS: In the NTS, CPP eliminated or attenuated the inhibition of these neurons induced by aortic nerve stimulation, but the inhibition induced by elevation of arterial pressure was not eliminated and the cardiac cycle-related rhythm of spontaneous discharge still existed. Whereas in the CVLM, CPP eliminated not only the inhibition of these neurons induced by aortic nerve stimulation, but the inhibition induced by blood pressure elevation and the cardiac cycle-related rhythm of spontaneous discharge disappeared. CONCLUSION: NMDA mechanism is importantly involved in the mechanism of baroreflex both in the NTS and in the CVLM; the barosensitive neurons in the NTS project to ipsilateral CVLM.
AIM: To study the roles of N-methyl-D-aspartate (NMDA) receptors in arterial baroreflex. METHODS: Experiments were performed in 17 urethane-anaesthetized male Sprague-Dawly rats. Twenty-seven rostral ventrolateral medulla (RVLM) neurons were electrophysiologically identified as putative presympathetic neurons. Responses of these neurons to baroreflex activation were used as an index to observe the effects of 3-(2-carboxypiperazin-4-yl) propyl-1-phosphonic acid (CPP) microinjected (0.1 microL, 50 mmol.L-1) into the nucleus tractus solitarii (NTS) or the caudal ventrolateral medulla (CVLM) ipsilaterally. RESULTS: In the NTS, CPP eliminated or attenuated the inhibition of these neurons induced by aortic nerve stimulation, but the inhibition induced by elevation of arterial pressure was not eliminated and the cardiac cycle-related rhythm of spontaneous discharge still existed. Whereas in the CVLM, CPP eliminated not only the inhibition of these neurons induced by aortic nerve stimulation, but the inhibition induced by blood pressure elevation and the cardiac cycle-related rhythm of spontaneous discharge disappeared. CONCLUSION:NMDA mechanism is importantly involved in the mechanism of baroreflex both in the NTS and in the CVLM; the barosensitive neurons in the NTS project to ipsilateral CVLM.