Presence of C-flanking peptide of neuropeptide Y(C-PON)-immunoreactive neurons in the olfactory cortex of the hedgehog (Erinaceus europaeus).

Although the presence of the neuropeptide C-terminal flanking peptide of neuropeptide Y, C-PON, has been described in the central nervous system (CNS) of mammals, to date there is no information related with its involvement in brain functions. An analysis of the location of C-PON in specific neuronal circuits of known anatomy and physiological action should provide light on its physiological role. The presence, distribution and morphology of C-PON-containing neurons in the olfactory cortex of the hedgehog was studied by immunocytochemistry. Immunoreactive neurons to C-PON were widely distributed in the three layers of the olfactory cortex of this primitive mammal. These neurons were medium sized and showed two or three immunostained, poorly branched, dendrites. In some positive neurons, a fine, beaded axon-like process was also immunostained. Although direct evidence of a physiological function of C-PON in the olfactory cortex of the hedgehog cannot be accurately stated from our findings, the morphology of C-PON neurons and their distribution in the deep cortical layers, where the majority of pyramidal neurons are located, suggest that this neuropeptide may play a role in the intrinsic neuronal circuitry of the relatively well-developed hedgehog paleocortex. A regulatory vascular role of some peptide-immunoreactive neurons can be inferred since occasional C-PON-positive neurons have been located near blood vessels.