Distribution and morphology of substance P-immunoreactive structures in the olfactory bulb and olfactory peduncle of the common marmoset (Callithrix jacchus), a primate species.

The present study describes the morphology and distribution of substance P-immunoreactive (SP-ir) elements in the olfactory bulb (OB) and olfactory peduncle (OP) of the common marmoset (Callithrix jacchus), a primate species. SP-ir neurons are very abundant in the OB and belong to two types. External tufted cells are present in the glomerular layer (GL), whereas granule cells are found in the deeper layers, especially in the granule cell layer (GRL), but also scattered in the OP. SP-ir fibers, putatively of central origin, were identified in the OP. They ascend into the bulbar layers. The SP-chemoarchitecture of the marmoset OB and OP does not differ more from rat, guinea pig and cat, than the SP-chemoarchitecture of these species varies among one another.