Dopaminergic Neurons in the Olfactory Bulb: A Differences in the Insectivore and Rodents

Jeong, Young Gil; Lee, Nam Seob; Won, Moo Ho

Abstract

These studies document species differences in the distribution of the catecholamine-synthesizing enzyme tyrosine hydroxylase (TH) within the main olfactory bulb (MOB) of a number of rodents and insectivore species including the rat, wild mouse, mongolian gerbil, stripped field mouse (apodemus agrarius), hedgehog, mole, laboratory shrew (suncus murinus). TH-containing neuronal perikarya were observed in the MOB of the both species of the rodents and insectivore except the hedgehog and laboratory shrew (suncus murinus). None of these cell groups displayed either dopamine beta hydroxylase (DBH) or phenylethanolamine-N-methyltransferase (PNMT). The number of stained somata and their intensity varied such that label was most prominent in the stripped field mouse followed in decreasing order by the rat, mongolian gerbil, wild mouse and mole. The vast majority of such cells occurred in the glomerular layer as periglomerular cells surrounging the glomeruli of the stripped field mouse, rat, mongolian gerbil, wild mouse and moles. Numerous additional cells were present in the external plexiform layer (EPL) and mitral cell layer (MCL). These often displayed long ascending immunoreactive processes and appeared to correspond to tufted cells. Also a few smaller, multipolar cells were present in the internal granular layer scattered among the granule cells. However, the hedgehog and laboratory shrew displayed no perikaryal staining in the MOB. In conclusion, these data suggest that TH is present in the MOB of stripped field mouse, rat, mongolian gerbil, wild mouse and moles but is not found in the MOB of the hedgehog and laboratory shrew, or that species differences exist in the level of TH.