Area postrema glutamate receptors mediate respiratory and gastric responses in the rabbit

The role of NMDA and non-NMDA receptors of the area postrema (AP) in the control of respiration and gastric motility was investigated in anaesthetized rabbits using microinjections (10-20 nl) of specific agonists or antagonists. NMDA (20 mM) or AMPA (10 mM) caused excitatory effects on respiration and gastric relaxation. Selective blockade of NMDA or non-NMDA receptors, respectively with D(-)-2-amino-5-phosphonopentanoic acid (D-AP5; 10 mM) and 6-nitro-7-sulphamoylbenzo(f)quinoxaline-2,3-dione (NBQX; 5 mM), decreased respiratory frequency and increased gastric tone. Both these effects were more marked following non-NMDA receptor blockade and were prevented by vagotomy. These findings show that NMDA and non-NMDA receptors are present on AP neurones and have a role in the tonic control of respiration and gastric motility.