Chronic intermittent hypoxia alters main olfactory bulb activity and olfaction

• Published in: Experimental neurology 2021-06, Vol.340, p.113653-113653, Article 113653
• Main Authors: Hernández-Soto, Rebeca, Villasana-Salazar, Benjamín, Pinedo-Vargas, Laura, Peña-Ortega, Fernando
• Format: Article
• Language: English
• Subjects: Buried food test; Chronic intermittent hypoxia; Habituation/dishabituation test; Main olfactory bulb; Network activity; Obstructive sleep apnea; Olfactory dysfunction
• ISSN: 0014-4886; 1090-2430
• DOI: 10.1016/j.expneurol.2021.113653

Olfactory dysfunction is commonly observed in patients with obstructive sleep apnea (OSA), which is related to chronic intermittent hypoxia (CIH). OSA patients exhibit alterations in discrimination, identification and odor detection threshold. These olfactory functions strongly rely on neuronal processing within the main olfactory bulb (MOB). However, a direct evaluation of the effects of controlled CIH on olfaction and MOB network activity has not been performed. Here, we used electrophysiological field recordings in vivo to evaluate the effects of 21-day-long CIH on MOB network activity and its response to odors. In addition, we assessed animals´ olfaction with the buried food and habituation/dishabituation tests. We found that mice exposed to CIH show alterations in MOB spontaneous activity in vivo, consisting of a reduction in beta and gamma frequency bands power along with an increase in the theta band power. Likewise, the MOB was less responsive to odor stimulation, since the proportional increase of the power of its population activity in response to four different odorants was smaller than the one observed in control animals. These CIH-induced MOB functional alterations correlate with a reduction in the ability to detect, habituate and discriminate olfactory stimuli. Our findings indicate that CIH generates alterations in the MOB neural network, which could be involved in the olfactory deterioration in patients with OSA. •Chronic intermittent hypoxia (CIH) increases slow (theta band power) main olfactory bulb (MOB) spontaneous network activity.•CIH decreases fast (beta and gamma bands power) MOB spontaneous network activity.•CIH decreases the broadband change in MOB network activity induced by odors.•CIH alters olfaction, reducing odor detection and discrimination, as well as olfactory memory.