Effects of NMDA on respiratory neurons in newborn rat medulla in vitro.

In 30 brain stem-spinal cord preparations isolated from newborn rats, we examined effects of 10 microM N-methyl-D-aspartate (NMDA) on 21 pre-inspiratory (Pre-I) and 26 inspiratory (I) neurons during perfusion in a synaptic blockade (low Ca2+, high Mg2+) bath, referred to here as low Ca. Application of NMDA to 9 Pre-I neurons that burst rhythmically by NMDA. Application of NMDA had no effect on 20 I neurons out of 26 tested. NMDA made one I neuron that was otherwise silent burst rhythmically in low Ca. The results suggest that, in this preparation, activation of NMDA receptors could contribute to induction or facilitation of burst activity by respiratory neurons, especially Pre-I neurons.