Effects of NMDA and non-NMDA receptor antagonists on inspiratory neurons in the in vitro brainstem-spinal cord preparation of newborn rat.

We examined the effects of N-methyl-D-aspartate (NMDA) antagonists, 2-amino-5-phosphonovaleric acid (APV) and non-NMDA antagonists, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) on inspiratory neurons in the medulla oblongata and C4 and C5 ventral root activity in the in vitro brainstem-spinal cord preparation of newborn rats. Application of APV induced increased rate of inspiratory neuron bursts, and decreased burst duration. The C4 burst activity was almost abolished by application of CNQX, whereas inspiratory neurons continued to discharge rhythmically. The results suggest that non-NMDA receptors are not crucially involved in the medullary respiratory rhythmogenesis, and that NMDA-mediated neurotransmission could modify the respiratory pattern, in the in vitro model.