Contribution of NMDA Receptors to Activity of Augmenting Expiratory Neurons in Vagotomized Cats

Abstract

To identify the NMDA receptor-mediated mechanism in augmenting expiratory(E2)neurons, the effects of systemic and local application of dizocilpine on spontaneous and evoked postsynaptic potentials(PSPs)were investigated in decerebrate and vagotomized cats.Intravenously applied dizocilpine reduced the inhibitory PSPs during inspiration and stage 1 expiration, but had little effect on the excitatory PSPs during stage 2 expiration.Iontophoresed dizocilpine caused a continuous hyperpolarization throughout the respiratory cycle.Dizocilpine had no effect on vagally evoked PSPs.These results suggest that the NMDA mechanisms are involved presynaptically in periodic postsynaptic inhibitions and postsynaptically in tonic excitation in E2 neurons.