OLFACTORY NERVE-STIMULATION ACTIVATES RAT MITRAL CELLS VIA NMDA AND NON-NMDA RECEPTORS IN-VITRO

THE neurotransmitter(s) and receptors mediating excitatory transmissio n at the mammalian olfactory nerve-mitral cell synapse were investigat ed using extracellular recordings in rat olfactory bulb slices. Single shocks applied to the olfactory nerve elicited both a short latency a nd a delayed excitatory response in mitral cells. Both responses were blocked after bath application of kynurenic acid, a broad-spectrum glu tamate receptor antagonist, or DNQX, a preferential non-NMDA receptor antagonist. The specific NMDA receptor antagonist AP5 selectively atte nuated the delayed, but not the initial excitation. These results sugg est that glutamate is the major excitatory transmitter in the mammalia n olfactory nerve, and excites mitral cells via NMDA and non-NMDA rece ptors.