Behavior of KCNQ Channels in Neural Plasticity and Motor Disorders

The broad distribution of voltage-gated potassium channels (VGKCs) in the human body makes them a critical component for the study of physiological and pathological function. Within the KCNQ family of VGKCs, these aqueous conduits serve an array of critical roles in homeostasis, especially in neural tissue. Moreover, the greater emphasis on genomic identification in the past century has led to a growth in literature on the role of the ion channels in pathological disease as well. Despite this, there is a need to consolidate the updated findings regarding both the pharmacotherapeutic and pathological roles of KCNQ channels, especially regarding neural plasticity and motor disorders which have the largest body of literature on this channel. Specifically, KCNQ channels serve a remarkable role in modulating the synaptic efficiency required to create appropriate plasticity in the brain. This role can serve as a foundation for clinical approaches to chronic pain. Additionally, KCNQ channels in motor disorders have been utilized as a direction for contemporary pharmacotherapeutic developments due to the muscarinic properties of this channel. The aim of this study is to provide a contemporary review of the behavior of these channels in neural plasticity and motor disorders. Upon review, the behavior of these channels is largely dependent on the physiological role that KCNQ modulatory factors (i.e., pharmacotherapeutic options) serve in pathological diseases.

Novel Approaches, Drug Candidates, and Targets in Pain Drug Discovery

Because of the problems associated with opioids, drug discovery efforts have been employed to develop opioids with reduced side effects using approaches such as biased opioid agonism, multifunctional opioids, and allosteric modulation of opioid receptors. Receptor targets such as adrenergic, cannabinoid, P2X3 and P2X7, NMDA, serotonin, and sigma, as well as ion channels like the voltage-gated sodium channels Nav1.7 and Nav1.8 have been targeted to develop novel analgesics. Several enzymes, such as soluble epoxide hydrolase, sepiapterin reductase, and MAGL/FAAH, have also been targeted to develop novel analgesics. In this review, old and recent targets involved in pain signaling and compounds acting at these targets are summarized. In addition, strategies employed to reduce side effects, increase potency, and efficacy of opioids are also elaborated. This review should aid in propelling drug discovery efforts to discover novel analgesics.

Spinal Actions of the NSAID Diclofenac on Nociceptive Transmission in Comparison to the Kv7 Channel Opener Flupirtine

NSAIDs are the drugs most commonly used to alleviate pain. Despite being a heterogeneous group of compounds, all of them share a mechanism of action based on blockade of COXs enzymes, which confers them anti-inflammatory and analgesic properties. Diclofenac is a NSAID with preferred activity on COX-2 isozymes, but additionally, other targets may be implicated in its analgesic activity. Among them, diclofenac may facilitate the activity of K_v7 channels, that have been previously recognized as potential therapeutic targets in analgesia. In this study, the antinociceptive actions of diclofenac acting at the spinal level and the role of K_v7 channels in its effects were evaluated. Electrophysiological recordings of spinal reflexes and responses of dorsal horn neurons were obtained using in vitro spinal cord preparations from neonatal mice. Diclofenac, applied at clinically relevant concentrations to the entire preparation, depressed wind-up of spinal reflexes with a pattern similar to that of flupirtine, an analgesic with activity as K_v7 channel opener. Depressant actions of both compounds were strongly reduced after K_v7 channel blockade with XE-991, indicating the implication of these channels in the observed effects. Flupirtine, but not diclofenac, also reduced action potential firing of dorsal horn neurons in response to electrical activation of nociceptive afferents, suggesting differences in the actions of both compounds on K_v7 channel configurations present in sensory areas of the cord. Results demonstrate previously unknown central actions of diclofenac on K_v7 channels located in spinal circuits, expanding the knowledge about its pharmacological actions.