Olfactory tract transection enhances adult neurogenesis in piriform cortex

Abstract

Adult neurogenesis happens continuously in olfactory bulb. Loss of sensory input to the olfactory bulb leads to decreased formation of new neurons in the bulb. Piriform cortex receives projection from ipsilateral olfactory bulb, and previous studies proved the existence of new neurons in adult piriform cortex under physiological conditions. However the effects of olfactory bulb input deprivation on adult neurogenesis in rat piriform cortex have not been investigated before. The existence of neuronal progenitor cells in adult rat piriform cortex were confirmed with Bromodeoxyuridine (BrdU) labeling and early neuronal markers such as doublecortin (DCX) and Polysialic Acid-NCAM (PSA-NCAM). Sensory deprivation to the piriform cortex achieved by transection of the olfactory tract at the caudal part of one olfactory bulb, before the frontal sinus, leads to a significant increase (~60%) of doublecortin positive cells in the ipsilateral piriform cortex compared with the contralateral (intact) side. Because deafferentation causes cell apoptosis, it is possible that deafferentation or local cell death can enhance the recruitment of new neurons in the piriform cortex.