Akira Haji, Mari Okazaki and Ryuji Takeda
Department of Pharmacology, Faculty of Medicine, Toyama Medical and Pharmaceutical
University,
2630 Sugitani, Toyama 930-0194, Japan
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ﾊ1 expiration,
but had little effect on the excitatory PSPs during stageﾊ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.
Keywords: Respiratory neuron, Intracellular recording, NMDA receptor