Non-NMDA receptors within caudal ventrolateral medulla are involved in transmission of baroreflex of rats.

AIM: To investigate the role of non N-methyl-D-aspartate acid (non-NMDA) receptors within the caudal ventrolateral medulla (CVLM) in mediating the baroreflex. METHODS: In urethane-anesthetized, paralyzed, and artificially ventilated rats, the effects of 6-cyano-7-nitroquinoxaline-2,3-dinoe (CNQX, a selective non-NMDA receptors antagonist) locally injected into the CVLM on the depressor responses evoked by aortic nerve stimulation and the barosensitivity of the rostral ventrolateral medulla (RVLM) barosensitive neurons were observed. RESULTS: Bilateral microinjection of CNQX (200 pmol in 100 nL for each side) into the CVLM significantly (P<0.01) increased the blood pressure (BP) and heart rate, and markedly (P<0.01) attenuated the depressor response to the aortic nerve stimulation. CNQX (200 pmol in 100 nL) unilaterally injected into the CVLM significantly (P<0.01) increased the firing rate of the ipsilateral RVLM barosensitive neurons and reduced the inhibitory responses of neurons evoked by stimulation of aortic nerve and elevation of BP, and partially inhibited the neuronal cardiac cycle-related rhythm. CONCLUSION: The CVLM played an important role in maintaining the tonic excitatory cardiovascular activities and transmitting the baroreceptor information via activation of non-NMDA receptors.