AUTHOR=Bullmann Torsten , Feneberg Emily , Kretzschmann Tanja Petra , Ogunlade Vera , Holzer Max , Arendt Thomas 

TITLE=Hibernation Impairs Odor Discrimination – Implications for Alzheimer’s Disease

JOURNAL=Frontiers in Neuroanatomy

VOLUME=Volume 13 - 2019

YEAR=2019

URL=https://www.frontiersin.org/journals/neuroanatomy/articles/10.3389/fnana.2019.00069

DOI=10.3389/fnana.2019.00069

ISSN=1662-5129

ABSTRACT=Reversible formation of PHF-like phosphorylated tau an early feature of Alzheimer´s disease (AD) was previously shown to occur in torpor during hibernation of Syrian hamsters. Here, we tackled the question to what extend hibernating Syrian hamsters can serve as a model for for the early stage of AD. During early AD  , anosmia, the loss of olfactory function, is a common and typical feature. We, thus, investigated tau phosphorylation, synaptic plasticity and behavioral physiology of the olfactory system during hibernation. Tau was phosphorylated on several AD -relevant epitopes, and distribution of PHF-like phosphorylated tau in the olfactory bulb was quite similar to what is seen in AD. Tau phosphorylation was not associated with a destabilization of microtubules or actin filaments and did not lead to fibril formation. Previously we observed a transient spine reduction in pyramidal cells in the hippocampus, which is correlated to the distribution of phosphorylated tau. Consistently, in the olfactory bulb the granule cells, which are devoid of phosphorylated tau, do not show a reduction in their spines. Contrary to previous reports no reduction in synaptic proteins was observed. However, when the effect of hibernation on olfactory memory was tested using a two odor discrimination task, non-hibernating animals showed a significant preference for the odor presented with a food reward, whereas hibernating animals did not. We conclude that hibernation is associated with a specific olfactory memory deficit, which might not be attributed to the formation of PHF-like phosphorylated tau within the olfactory bulb. We discuss a possible involvement of modulatory input provided by cholinergic neurons in the basal forebrain, which are affected by hibernation.