PRESYNAPTIC COLOCALIZATION OF CARNOSINE AND GLUTAMATE IN OLFACTORY NEURONS

OLFACTION plays a dominant role in modulating behaviour in most verteb rate species and the olfactory bulb is considered a model system for c haracterizing principles of neural computation. Nevertheless, although the physiology and neurochemistry of the olfactory circuits have been widely studied, the neurotransmitter released by olfactory receptor n eurones remains unknown. We now describe the ultrastructural localizat ion of the dipeptide carnosine and the excitatory amino acid glutamate in the glomerular layer of the mouse olfactory bulb. We demonstrate t hat both carnosine-like and glutamate-like immunoreactivities are sele ctively co-localized in the olfactory neurone boutons. These observati ons, taken with the recent findings of glutamate-receptor subunit expr ession in rodent olfactory bulb, argue compellingly for a roIe of glut amate in olfactory neurotransmission and suggest a modulatory effect o f carnosine.