SOME NORADRENERGIC NEURONS OF LOCUS-CERULEUS OLFACTORY PATHWAYS CONTAIN NEUROPEPTIDE-Y

We report a specific tracing technique for studying projections of nor adrenergic neurons that contain other transmitters. Autoradiography af ter retrograde axonal transport of tritiated-noradrenaline ([H-3]NA) w as combined with immunocytochemical detection of endogeneous NA or neu ropeptide Y (NPY). The specificity of [H-3]NA retrograde labeling was dependent on the concentration of [H-3]NA injected at the terminal reg ion. At 2 x 10(-3) M, the specificity of [H-3]NA retrograde labeling w as confirmed by immunodetection of endogenous NA in radiolabeled cell bodies of the locus ceruleus. Combination of autoradiography of [H-3]N A retrograde labeling with immunodetection of NPY demonstrated that a some scattered locus ceruleus noradrenergic neurons (about 26%) projec ting to the olfactory bulb do contain NPY.