Pharmacological properties of peripherally induced postsynaptic potentials in bulbar respiratory neurons of decerebrate cats.

Intracellular recordings of bulbar inspiratory and post-inspiratory neurons, combined with extracellular iontophoresis of antagonists of putative neurotransmitters, were performed in decerebrate cats. Inhibitory postsynaptic potentials (IPSPs) evoked by stimulation of the superior laryngeal nerve or vagus nerve were depressed by bicuculline in all 22 neurons tested, but not modified by strychnine. The non-N-methyl-D-aspartate (NMDA) glutamate antagonist 6,7-dinitroquinoxaline-2,3-dione (DNQX) decreased the neurally evoked excitatory postsynaptic potentials (EPSPs) in 23 out of 26 neurons tested, while the NMDA antagonist dizocilpine had no notable effect. The present results suggest that the peripherally induced IPSPs are mediated through gamma-aminobutyric acid (GABA)A receptors and the EPSPs through non-NMDA glutamate receptors in bulbar respiratory neurons.