In Vivo Recording of Ascorbate and Neural Excitability in Medial Vestibular Nucleus and Hippocampus Following Ice Water Vestibular Stimulation in Rats

Hydrogen-Bonded Organic Framework Enhanced Antifouling Property for Efficient In Situ Electrochemical Assay of Cerebral Ascorbic Acid

Accurate determination of cerebral ascorbic acid (AA) is crucial for understanding ischemic stroke (IS) related pathological events. Carbon fiber microelectrodes (CFEs) have proven to be robust tools with high sensitivity toward AA, however, they face ongoing challenges for in situ measurement due to the non-specific adsorption of proteins in brain tissue. In this study, the hydrogen-bonded organic framework PFC-71 is synthesized and modified on CFEs through π-π stacking interactions with carboxylated carbon nanotubes (CNT-COOH). It is found that the gating effect and hydrophilicity of PFC-71 provided the CFE with excellent antibiofouling properties. As a result, AA exhibited a low oxidation potential of -30 mV on the CFE/CNT-COOH/PFC-71, even in the presence of 20 mg mL-1 bovine serum albumin. Given the structural advantages of CFE/CNT-COOH/PFC-71, a ratiometric electrochemical strategy for AA is established, enabling the in situ assay of cerebral AA in a middle cerebral artery occlusion (MCAO) model with high accuracy and stability.

COF-Coated Microelectrode for Space-Confined Electrochemical Sensing of Dopamine in Parkinson's Disease Model Mouse Brain

Parkinson's disease (PD) is a progressive neurodegenerative disorder causing the loss of dopaminergic neurons in the substantia nigra and the drastic depletion of dopamine (DA) in the striatum; thus, DA can act as a marker for PD diagnosis and therapeutic evaluation. However, detecting DA in the brain is not easy because of its low concentration and difficulty in sampling. In this work, we report the fabrication of a covalent organic framework (COF)-modified carbon fiber microelectrode (cCFE) that enables the real-time detection of DA in the mouse brain thanks to the outstanding antibiofouling and antichemical fouling ability, excellent analytical selectivity, and sensitivity offered by the COF modification. In particular, the COF can inhibit the polymerization of DA on the electrode (namely, chemical fouling) by spatially confining the molecular conformation and electrochemical oxidation of DA. The cCFE can stably and continuously work in the mouse brain to detect DA and monitor the variation of its concentration. Furthermore, it was combined with levodopa administration to devise a closed-loop feedback mode for PD diagnosis and therapy, in which the cCFE real-time monitors the concentration of DA in the PD model mouse brain to instruct the dose and injection time of levodopa, allowing a customized medication to improve therapeutic efficacy and meanwhile avoid adverse side effects. This work demonstrates the fascinating properties of a COF in fabricating electrochemical sensors for in vivo bioanalysis. We believe that the COF with structural tunability and diversity will offer enormous promise for selective detection of neurotransmitters in the brain.

Role of inferior colliculus in vestibular vertigo induced by water caloric irrigation

Background: Vestibular vertigo is a common clinical symptom; however, the central neural mechanism of it is still poorly understood.Objective: To demonstrate the changes of neural excitability and ascorbate in inferior colliculus (IC) in a rat vertigo model induced by water caloric irrigation.Methods: In vertigo model induced by water caloric irrigation, we recorded the changes of spontaneous firing rate (SFR) of IC. Then a technique that combining in vivo microanalysis with an online electrochemical system (OECS) was employed to monitor the changes of extracellular ascorbate in IC.Results: Electrophysiological studies showed that after vestibular ice water stimulation, the level of SFR in IC significantly increased, reaching (989 ± 9) % and (941 ± 62) % respectively at 2.0 h after contralateral ice water vestibular stimulation and ipsilateral ice water vestibular stimulation. However, the level of ascorbate in IC dramatically decreased after ice stimulation, decreased to (30 ± 12) % and (57 ± 24) % of the basal level respectively in the contralateral group and ipsilateral group.Conclusions and significance: These findings suggest that inferior colliculus plays a role in peripheral vertigo, which would appear useful for uncovering neural mechanisms of vertigo and help finding novel therapeutic targets for vertigo.