The olfactory mucosa, first actor of olfactory detection, is sensitive to glucocorticoid hormone

Abstract

The olfactory mucosa (OM) is the primary site of odorant detection, and its axonal projections relay information to brain structures for signal processing. We have previously observed that olfactory function can be affected during a prolonged stress challenge in Wistar rats. The stress response is a neuroendocrine retro‐controlled loop allowing pleiotropic adaptive tissue alterations, which are partly mediated through the release of glucocorticoid hormones. We hypothesised that, as part of their wide‐ranging pleiotropic effects, glucocorticoids might affect the first step of olfactory detection. To study this, we used a number of approaches ranging from the molecular detection and functional characterisation of glucocorticoid receptors (GRs) in OM cells, to the study of GR acute activation in vivo at the molecular, electrophysiological and behavioural levels. In contrast to previous reports, where GR was reported to be exclusive in olfactory sensory neurones, we located functional GR expression mostly in olfactory ensheathing cells. Dexamethasone (2 mg/kg) was injected intraperitoneally to activate GR in vivo, and this led to functional odorant electrophysiological response (electro‐olfactogram) and OM gene expression changes. In a habituation/cross‐habituation test of olfactory sensitivity, we observed that DEX‐treated rats exhibited higher responsiveness to a complex odorant mixture. These findings support the idea that olfactory perception is altered in stressed animals, as glucocorticoids might enhance odour detection, starting at the first step of detection.

Targeted Suppression of Lipoprotein Receptor LSR in Astrocytes Leads to Olfactory and Memory Deficits in Mice

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Early and Late Transcriptional Changes in Blood, Neural, and Colon Tissues in Rat Models of Stress-Induced and Comorbid Pain Hypersensitivity Reveal Regulatory Roles in Neurological Disease

“…Two olfactory receptors , Olr35 and Olr63 , were 2-fold more expressed in SIH rats compared to naïve. Olfactory perception is affected in stressed animals, as glucocorticoids might enhance odor detection, starting at the first step of detection ( 41 ).…”

Modulation of olfactory signal detection in the olfactory epithelium: focus on the internal and external environment, and the emerging role of the immune system

“…This switch prioritizes pathogen removal involving massive immune cell recruitment and activation of nuclear factor-κB (NFkB) in basal cells Antagonism or synergy between different messengers certainly exists. For example, the perception of odors can be influenced by stress and the inner emotional state of the animal (Raynaud et al 2015;Bombail 2019;Meunier et al 2020). Many experiments using anesthesia, animal manipulation, and intranasal instillation may induce stress and thus interact with the studied modulator.…”

“…In addition, the maternal gestational stress linked to an abrupt dietary transition from non-odorized to odorized food might also stress the pups and lead to a decrease in the OSN response to odorants as demonstrated for animals raised in unpredictable stress conditions (Raynaud et al 2015). The effect of stress on the OE may be linked to the effect of glucocorticoids affecting this neuroepithelium (Meunier et al 2020). Studies dealing with environmental modulations of OSN activity may thus also consider internal factors which are presented in the next section.…”