In vivo measurement of the dynamics of norepinephrine in an olfactory bulb following ischemia-induced olfactory dysfunction and its responses to dexamethasone treatment

Network pharmacology and experimental validation reveal the mechanisms of sniffing essential oil of Acori Tatarinowii rhizoma in treating olfactory dysfunction

ETHNOPHARMACOLOGICAL RELEVANCE

Acorus tatarinowii Rhizoma, a traditional Chinese medicine known for open the orifices and transform phlegm, is used in the treatment of brain disorders. The essential oil of Acorus tatarinowii Rhizoma (EOAT) has demonstrated neuroprotective properties clinically. However, research into its effect on Olfactory Dysfunction (OD) remains limited.

AIM OF THE STUDY

This study aimed to investigate the effects and mechanisms of sniffing EOAT on improving olfactory function in a 3-Methylindole (3-MI)-induced OD mouse model.

MATERIALS AND METHODS

The research involved intraperitoneal injection of 3-MI to induce OD in mice. The effects of EOAT treatment were assessed on olfactory function, olfactory bulb (OB) pathology, inflammatory factors, olfactory marker protein (OMP), microglial activation, and related pathway proteins and mRNA.

RESULTS

Based on the GC-MS analysis results of EOAT and network pharmacology studies, we predicted 18 targets associated with the treatment of OD. SLC6A3, MAOB, DRD1, and PTGS2 were identified as the core targets of EOAT against OD. Molecular docking and KEGG enrichment results indicated that EOAT may exert anti-inflammatory effects by acting on the core target PTGS2, with its anti-inflammatory mechanism possibly related to the PI3K/Akt signaling pathway. Subsequent animal experiments confirmed that inhalation of EOAT significantly increased the body weight of OD model mice, shortened the foraging time, enhanced the expression of OMP in OB, reduced damage to the OB cells, and improved olfactory function. Meanwhile, EOAT significantly alleviated the inflammatory response in OB of OD model mice, inhibited the activation of microglial cells, and suppressed the expression of PI3K/Akt signaling pathway proteins and mRNA.

CONCLUSION

EOAT inhalation could improve olfactory function in 3-MI-induced OD model. The underlying mechanism may be related to the modulation of the PI3K/Akt signaling pathway.

Brain interstitial fluid drainage and extracellular space affected by inhalational isoflurane: in comparison with intravenous sedative dexmedetomidine and pentobarbital sodium

Brain interstitial fluid drainage and extracellular space are closely related to waste clearance from the brain. Different anesthetics may cause different changes of brain interstitial fluid drainage and extracellular space but these still remain unknown. Herein, effects of the inhalational isoflurane, intravenous sedative dexmedetomidine and pentobarbital sodium on deep brain matters' interstitial fluid drainage and extracellular space and underlying mechanisms were investigated. When compared to intravenous anesthetic dexmedetomidine or pentobarbital sodium, inhalational isoflurane induced a restricted diffusion of extracellular space, a decreased extracellular space volume fraction, and an increased norepinephrine level in the caudate nucleus or thalamus with the slowdown of brain interstitial fluid drainage. A local administration of norepinephrine receptor antagonists, propranolol, atipamezole and prazosin into extracellular space increased diffusion of extracellular space and interstitial fluid drainage whilst norepinephrine decreased diffusion of extracellular space and interstitial fluid drainage. These findings suggested that restricted diffusion in brain extracellular space can cause slowdown of interstitial fluid drainage, which may contribute to the neurotoxicity following the waste accumulation in extracellular space under inhaled anesthesia per se.