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

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Abstract
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-sulphamoyl-benzo(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.