https://orcid.org/0000-0003-4615-100X
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Abstract
The main and accessory olfactory bulbs (MOB and AOB) are unique in that they produce new neurons throughout adulthood. Despite the recent knowledge about the involvement of postnatally generated cells in several aspects of olfaction, the functional role of these neurons is still not sufficiently understood. The function of newly generated olfactory bulb neurons is primarily investigated in relation to activities related to smell. Stress-induced activation of new olfactory neurons has not yet been studied. Thus, our work was aimed to investigate whether a stressful event, such as maternal separation (MS) can induce Fos expression in postnatally-born neurons in the MOB and AOB. Rat pups were exposed to single maternal separation (SMS) for 2 h at the postnatal days: P7, P14, and P21. Quantification of immunohistochemically labeled Fos + cells revealed that exposure to SMS in different age stages during the first postnatal month stimulates activity in cells of individual MOB/AOB layers in an age-dependent manner. In order to find out whether newly generated cells in the MOB/AOB could express Fos protein as a response to SMS, newborn rats were administrated with the marker of proliferation, bromodeoxyuridine (BrdU) at P0, and three weeks later (at P21) colocalization of Fos and BrdU in the neurons of the MOB and AOB was assessed. Quantitative analysis of BrdU/Fos double-labeled cells showed that Fos is expressed only in a small number of postnatally generated cells within the MOB/AOB. Our results indicate that postnatally generated MOB/AOB neurons are less sensitive to stress caused by MS than preexisting ones.
Our results showed that single maternal separation (SMS) is a stressful event that in age-dependent manner stimulates cellular activity in the main and accessory olfactory bulb (AOB) – the structures dedicated to odor information processing. The low level of Fos expression in newborn neurons of the main and accessory bulb indicates that postnatally generated cells are less sensitive to neonatal stress than preexisting neurons.
LAY SUMMARY
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Notes on contributors
Monika Závodská
Monika Závodská, Dr. rer. nat., PhD. is a young researcher at the Department of Regenerative Medicine and Cell Therapy of the INb BMC SAS, Slovakia. She is experienced in morphological analysis of the CNS and in quantitative and image analysis.
Kamila Fabianová
Kamila Fabianová, Dr. rer. nat., PhD. is a young researcher at the Department of Regenerative Medicine and Cell Therapy of the INb BMC SAS, Slovakia. Her research is focused on the effect of environmental factors on postnatal neurogenesis in the olfactory neurogenic region and corresponding behavioral changes.
Marcela Martončíková
Marcela Martončíková, Dr. rer. nat., PhD. is senior researcher at the Department of Regenerative Medicine and Cell Therapy of the INb BMC SAS, Slovakia. She is an expert in the field of postnatal neurogenesis and developmental studies in the olfactory system.
Adam Raček
Adam Raček, DVM., PhD. is a postdoctoral fellow at the Department of Anatomy, Histology and Physiology, University of Veterinary Medicine and Pharmacy in Košice. He finished his PhD in the Neuroscience. His research is oriented on adult neurogenesis in relation to the pathogenesis of neurodegenerative diseases.
Enikő Račeková
Enikő Račeková, Dr rer. nat., PhD. is the Head of the Laboratory of Neuromorphology and Developmental Neurobiology of the INb BMC, SAS in Košice, Slovakia. Her research team focuses on investigation the processes of postnatal neurogenesis in the rat olfactory system under physiological and pathological conditions.