Voltage-gated Na(+) channels in chemoreceptor afferent neurons--potential roles and changes with development

The ability of Ibutropin to blunt fentanyl-induced respiratory depression is independent of its activation of carotid body chemoafferents

This study examined the effects of intravenous injection of isobutyric tropine ester (Ibutropin) on ventilation in freely-moving sham-operated (SHAM) male Sprague Dawley rats and those with bilateral carotid sinus nerve transection (CSNX). This study also examined the effects of a subsequent injection of fentanyl on ventilatory parameters in both groups of rats. Ibutropin (200 μmol/kg, i.v.) elicited rapid and pronounced increases in breathing frequency, tidal volume, minute ventilation, peak inspiratory and expiratory flows, and inspiratory and expiratory drives in SHAM rats, but substantially smaller responses in CSNX rats. The subsequent injection of fentanyl (75 μg/kg, i.v.) elicited similar ventilatory responses in Ibutropin-treated SHAM and CSNX rats with markedly different changes in end-inspiratory and end-expiratory pauses, expiratory delay, and apneic pause. Moreover, the fentanyl-induced responses in Ibutropin-treated SHAM and CSNX rats were substantially smaller than in rats that were pre-injected with vehicle (saline) rather than Ibutropin. These novel findings suggest that Ibutropin acts at the carotid body-chemoafferent complex to drive ventilation by mechanisms that may involve the rapid entry of this cell-permeant tropine ester into chemoafferent nerve terminals and/or primary glomus cells. A key finding was that the ability of Ibutropin to blunt the adverse effects of fentanyl on breathing does not require functional carotid body chemoreceptor afferent input to brainstem structures controlling breathing. As such, the ability of Ibutropin to greatly diminish the adverse effects of fentanyl on breathing may involve the actions of Ibutropin within central respiratory control centers and/or peripheral structures other than the carotid bodies. SIGNIFICANCE STATEMENT: This study revealed that the ability of Ibutropin to blunt the respiratory depressant effects of fentanyl may involve mechanisms present in central respiratory control centers and/or peripheral structures other than the carotid bodies.

COVID-19-induced neurological symptoms: focus on the role of metal ions

Neurological symptoms are prevalent in both the acute and post-acute phases of coronavirus disease 2019 (COVID-19), and they are becoming a major concern for the prognosis of COVID-19 patients. Accumulation evidence has suggested that metal ion disorders occur in the central nervous system (CNS) of COVID-19 patients. Metal ions participate in the development, metabolism, redox and neurotransmitter transmission in the CNS and are tightly regulated by metal ion channels. COVID-19 infection causes neurological metal disorders and metal ion channels abnormal switching, subsequently resulting in neuroinflammation, oxidative stress, excitotoxicity, neuronal cell death, and eventually eliciting a series of COVID-19-induced neurological symptoms. Therefore, metal homeostasis-related signaling pathways are emerging as promising therapeutic targets for mitigating COVID-19-induced neurological symptoms. This review provides a summary for the latest advances in research related to the physiological and pathophysiological functions of metal ions and metal ion channels, as well as their role in COVID-19-induced neurological symptoms. In addition, currently available modulators of metal ions and their channels are also discussed. Collectively, the current work offers a few recommendations according to published reports and in-depth reflections to ameliorate COVID-19-induced neurological symptoms. Further studies need to focus on the crosstalk and interactions between different metal ions and their channels. Simultaneous pharmacological intervention of two or more metal signaling pathway disorders may provide clinical advantages in treating COVID-19-induced neurological symptoms.

Dynamics analysis of the hippocampal neuronal model subjected to cholinergic action related with Alzheimer's disease

There are evidences that the region of hippocampus is affected in the early stage of Alzheimer's disease (AD). Moreover, the hippocampal pyramidal neurons receive cholinergic input from the medial septum. Thus, this study, based on the results of electrophysiological experiments, first constructs a modified hippocampal CA1 pyramidal neuronal model by introducing two new currents of M-current and calcium ion-activated potassium ion current to depict the cholinergic input receiving from the medial septum, and then explores how acetylcholine deficiency and beta-amyloid accumulation under the pathological condition of AD influence the neuronal dynamics in terms of theta band power and spiking frequency using computational approach. By simulating acetylcholine potentiated M-current and calcium ion-activated potassium ion current, numerical results reveal that the relative theta band power increases significantly and the firing rate decreases obviously when acetylcholine is deficient. Similarly, by simulating beta-amyloid enhanced delay rectification potassium ion current, we also detect that the relative theta band power increases as well as the firing rate decreases remarkably as beta-amyloid is accumulated. In addition, the mechanism underlying these dynamical changes in theta rhythm and firing behavior is investigated by nonlinear behavioral analysis, which demonstrates that both deficiency in acetylcholine and accumulation in beta-amyloid can promote the emergence of stable equilibrium state in this modified hippocampal neuronal model. Note that acetylcholine deficiency together with beta-amyloid deposition plays key role in the pathogenesis of AD. We expect these findings could have important implications on better understanding pathogenesis and expounding potential biomarkers for AD.

Pain transduction: a pharmacologic perspective

INTRODUCTION

Pain represents a necessary physiological function yet remains a significant pathological process in humans across the world. The transduction of a nociceptive stimulus refers to the processes that turn a noxious stimulus into a transmissible neurological signal. This involves a number of ion channels that facilitate the conversion of nociceptive stimulus into and electrical signal.

AREAS COVERED

An understanding of nociceptive physiology complements a discussion of analgesic pharmacology. Therefore, the two are presented together. In this review article, a critical evaluation is provided on research findings relating to both the physiology and pharmacology of relevant acid-sensing ion channels (ASICs), transient receptor potential (TRP) cation channels, and voltage-gated sodium (Nav) channels. Expert commentary: Despite significant steps toward identifying new and more effective modalities to treat pain, there remain many avenues of inquiry related to pain transduction. The activity of ASICs in nociception has been demonstrated but the physiology is not fully understood. A number of medications appear to interact with ASICs but no research has demonstrated pain-relieving clinical utility. Direct antagonism of TRPV1 channels is not in practice due to concerning side effects. However, work in this area is ongoing. Additional research in the of TRPA1, TRPV3, and TRPM8 may yield useful results. Local anesthetics are widely used. However, the risk for systemic effects limits the maximal safe dosage. Selective Nav antagonists have been identified that lack systemic effects.