Substance P and tyrosine hydroxylase are localized in different neurons of the hamster olfactory bulb.

Both tyrosine hydroxylase (TH), the first enzyme in the catecholamine synthetic pathway, and substance P were localized previously to juxtaglomerular neurons in the hamster main olfactory bulb. These neurons had similar features and distribution suggesting that the enzyme, a marker for dopaminergic neurons, and the peptide transmitter, respectively, might coexist in the same cells. To determine if the two antigens occurred in the same neurons specific antibodies and a two color double label technique were utilized. Co-localization of the transmitters was not observed in any region of the olfactory bulb. In addition, interspecies differences were observed in the distribution of both TH and substance P labeled neurons which support the lack of co-localization in the double label studies. The data suggest that olfactory bulb neurons of similar morphology and distribution may synthesize different transmitters.