Heterogenous immunohistochemical expression of microglia-specific ionized calcium binding adaptor protein (Iba1) in the mouse olfactory bulb.

Glial cells regulate some neural functions which depend on the homeostatic maintenance of extracellular calcium within narrow physiological ranges. In this study, the presence of microglia-specific ionized calcium binding adaptor molecule 1 (Iba1) was examined in the mouse olfactory bulb. A heterogenous pattern of Iba1-positive cells expression was observed between the main and accessory olfactory bulbs (MOB and AOB, respectively). While Iba1 was almost uniformly expressed among the laminae of the MOB, its expression showed spatial variations from the anterior to the posterior regions of the AOB. Double immunofluorescence was used to confirm that Iba1 is not expressed in astrocytes which stained for glial fibrillary acidic protein. Since Iba1 may mediate calcium signals in microglia, the observations suggest a potential involvement of Iba1 and hence microglia in olfactory bulb function and/or homeostasis. Together with our previous observation, this provides further support of a bulbar neuron-glia system of potential physiological significance.