K+ Channel Modulatory Subunits KChIP and DPP Participate in Kv4-Mediated Mechanical Pain Control.

The K+ channel pore-forming subunit Kv4.3 is expressed in a subset of nonpeptidergic nociceptors within the dorsal root ganglion (DRG), and knockdown of Kv4.3 selectively induces mechanical hypersensitivity, a major symptom of neuropathic pain. K+ channel modulatory subunits KChIP1, KChIP2, and DPP10 are coexpressed in Kv4.3+ DRG neurons, but whether they participate in Kv4.3-mediated pain control is unknown. Here, we show the existence of a Kv4.3/KChIP1/KChIP2/DPP10 complex (abbreviated as the Kv4 complex) in the endoplasmic reticulum and cell surface of DRG neurons. After intrathecal injection of a gene-specific antisense oligodeoxynucleotide to knock down the expression of each component in the Kv4 complex, mechanical hypersensitivity develops in the hindlimbs of rats in parallel with a reduction in all components in the lumbar DRGs. Electrophysiological data further indicate that the excitability of nonpeptidergic nociceptors is enhanced. The expression of all Kv4 complex components in DRG neurons is downregulated following spinal nerve ligation (SNL). To rescue Kv4 complex downregulation, cDNA constructs encoding Kv4.3, KChIP1, and DPP10 were transfected into the injured DRGs (defined as DRGs with injured spinal nerves) of living SNL rats. SNL-evoked mechanical hypersensitivity was attenuated, accompanied by a partial recovery of Kv4.3, KChIP1, and DPP10 surface levels in the injured DRGs. By showing an interdependent regulation among components in the Kv4 complex, this study demonstrates that K+ channel modulatory subunits KChIP1, KChIP2, and DPP10 participate in Kv4.3-mediated mechanical pain control. Thus, these modulatory subunits could be potential drug targets for neuropathic pain.SIGNIFICANCE STATEMENT Neuropathic pain, a type of moderate to severe chronic pain resulting from nerve injury or disorder, affects 6.9%-10% of the global population. However, less than half of patients report satisfactory pain relief from current treatments. K+ channels, which act to reduce nociceptor activity, have been suggested to be novel drug targets for neuropathic pain. This study is the first to show that K+ channel modulatory subunits KChIP1, KChIP2, and DPP10 are potential drug targets for neuropathic pain because they form a channel complex with the K+ channel pore-forming subunit Kv4.3 in a subset of nociceptors to selectively inhibit mechanical hypersensitivity, a major symptom of neuropathic pain.

Mesenchymal stem cell exosomes as a cell-free therapy for nerve injury-induced pain in rats.

Nerve injury-induced neuropathic pain is difficult to treat. In this study, we used exosomes derived from human umbilical cord mesenchymal stem cell (UCMSC) as a cell-free therapy for nerve injury-induced pain in rats. Isolated UCMSC exosomes range in size from 30 to 160 nm and contain CD63, HSP60, and CD81 exosome markers. After L5/6 spinal nerve ligation surgery, single intrathecal injection of exosomes reversed nerve ligation-induced mechanical and thermal hypersensitivities of right hindpaw of rats at initial and well-developed pain stages. Moreover, continuous intrathecal infusion of exosomes achieved excellent preventive and reversal effects for nerve ligation-induced pain. In immunofluorescent study, lots of Exo-green-labelled exosomes could be found majorly in the ipsilateral L5 spinal dorsal horn, dorsal root ganglion, and peripheral axons, suggesting the homing ability of UCMSC exosomes. They also appeared in the central terminals or cell bodies of IB4, CGRP, and NF200 sensory neurons. In addition, exosome treatment suppressed nerve ligation-induced upregulation of c-Fos, CNPase, GFAP, and Iba1. All these data suggest that the analgesic effects of exosomes may involve their actions on neuron and glial cells. Exosomes also inhibited the level of TNF-α and IL-1ß, while enhanced the level of IL-10, brain-derived neurotrophic factor, and glial cell line-derived neurotrophic factor in the ipsilateral L5/6 dorsal root ganglion of nerve-ligated rats, indicating anti-inflammatory and proneurotrophic abilities. Protein analysis revealed the content of vascular endothelial growth factor C, angiopoietin-2, and fibroblast growth factor-2 in the exosomes. In summary, intrathecal infusion of exosomes from UCMSCs may be considered as a novel therapeutic approach for nerve injury-induced pain.

Continuous Intrathecal Infusion of Cannabinoid Receptor Agonists Attenuates Nerve Ligation-Induced Pain in Rats.

BACKGROUND AND OBJECTIVES: Cannabinoid receptors (CB1R/CB2R) are known to play important roles in pain transmission. In this study, we investigated the effects of continuous intrathecal infusion of CB1/2R agonists in the L5/6 spinal nerve ligation pain model. METHODS: Under isoflurane anesthesia, rats received nerve ligation and intrathecal catheter connected to an infusion pump. After surgery, saline (1 µL/h), CB1/2R agonist WIN55,212-2, CB1R agonist ACEA, or CB2R agonist AM1241 (1 µmol/h) was given intrathecally for 7 days. The mechanical and thermal sensitivities of rat hindpaw were determined by von Frey hair and radiant heat tests. The expression of CB1/2R and protein levels of CB1/2R, Iba1, glial fibrillary acidic protein, and tumor necrosis factor α were examined by immunofluorescence study and Western blotting. RESULTS: On postligation day 7, rats that received WIN55,212-2, ACEA or AM1241 had significantly higher mean withdrawal thresholds (6.8, 8.4, and 10.2 g) and latencies (6.3, 7.3, and 9.1 seconds) than did saline-treated rats (1.7 g, 2.2 seconds). Cannabinoid receptors were expressed not only in IB4 (isolectin B4) and CGRP (calcitonin gene-related peptide) dorsal root ganglion neurons, their central terminals, and peripheral axons, but also in neurons, microglia, and astrocytes in spinal cord. Cannabinoid receptor agonists enhanced nerve ligation-induced up-regulation of cannabinoid receptor in spinal cord and dorsal root ganglion. Treatment with WIN55,212-2 or AM1241, but not ACEA, markedly reduced nerve ligation-induced up-regulation of Iba1, glial fibrillary acidic protein, and tumor necrosis factor α in spinal cord. CONCLUSIONS: Continuous intrathecal infusion of CB1/2R agonists elicits antinociception in the pain model. The mechanisms might involve their actions on neurons and glial cells. CB2R, but not CB1R, seems to play an important role in the regulation of nerve injury-induced neuroinflammation.

Nerve growth factor-induced synapse-like structures in contralateral sensory ganglia contribute to chronic mirror-image pain.

Elevated nerve growth factor (NGF) in the contralateral dorsal root ganglion (DRG) mediates mirror-image pain after peripheral nerve injury, but the underlying mechanism remains unclear. Using intrathecal injection of NGF antibodies, we found that NGF is required for the development of intra-DRG synapse-like structures made by neurite sprouts of calcitonin gene-related peptide (CGRP(+)) nociceptors and sympathetic axons onto neurite sprouts of Kv4.3(+) nociceptors. These synapse-like structures are formed near NGF-releasing satellite glia surrounding large DRG neurons. Downregulation of the postsynaptic protein PSD95 with a specific shRNA largely eliminates these synapse-like structures, suppresses activities of Kv4.3(+) but not CGRP(+) nociceptors, and attenuates mirror-image pain. Furthermore, neutralizing the neurotransmitter norepinephrine or CGRP in the synapse-like structures by antibodies has similar analgesic effect. Thus, elevated NGF after peripheral nerve injury induces neurite sprouting and the formation of synapse-like structures within the contralateral DRG, leading to the development of chronic mirror-image pain.

Tracheal intubation condition--a comparison between one minute after rocuronium alone, one minute after rocuronium combined with atracurium and one minute after atracurium with rocuronium at one minute priming interval.

BACKGROUND: Rocuronium, a monoquaternary steroid analogue of vecuronium, is designed to provide a rapid onset of action. Experimentally, it has been shown that two non-depolarizing neuromuscular relaxants administered together can produce either a neuromuscular block of a size expected to be the sum of the individual doses (additive effect) or a larger neuromuscular block (synergistic effect). Experimental observations have suggested that during onset rocuronium acts synergistically with other nondepolarizing agents, but that at a steady state the combined action is additive. METHODS: To investigate whether rocuronium can speed up the onset of atracurium for intubation, 120 patients who consented to receive elective surgery requiring tracheal intubation were randomly assigned to 3 equally divided groups to receive one of the following three different combinations of muscle relaxants: twice ED95 of rocuronium (0.6 mg/kg group 1), an equipotent mixture of ED95 of rocuronium and atracurium (0.3 mg/kg and 0.25 mg/kg respectively, group 2), and rocuronium 0.1 mg/kg to prime atracurium 0.42 mg/kg at 1 min interval. Intubation conditions were assessed 1 minute after intravenous muscle relaxant injection, and scored as good, acceptable and poor based on four clinical evaluators: the ease of laryngoscopy (score of 1-3), the relaxation of vocal cord (1-3), the degree of coughing (1-3), and movement of extremity (1-3). Adding up together, intubation condition that scored 4-5 was considered to be good, 6-7 acceptable, and 8-12 poor. RESULTS: The conditions produced in the rocuronium and the mixture groups were similar and both were moderately better than those of the priming group. Good intubation conditions were achieved in 58% patients of the rocuronium group, 63% of the mixture group and 43% of the priming group. By Pearson Chi-square test, the comparisons did not show statistical significance between groups. CONCLUSIONS: Statistically, rocuronium alone, mixture of equipotent atracurium and rocuronium, and using rocuronium to prime atracurium all provided similar onset for satisfactory intubation.

Pneumoperitoneum complicated pneumomediastinum causing cardiovascular deterioration in a low-body-weight premature infant during laparoscopic Nissen fundoplication.

Due to smaller incisions, fewer wound injuries, and a shorter time of recovery, laparoscopic procedures are becoming increasingly popular in pediatric surgery, but the safety of their application in low-body-weight or premature infants should be a major concern. Here we present a case report of a 3-month-old premature infant, who developed a sudden change of hemodynamic instability while undergoing a laparoscopic Nissen's fundoplication for gastroesophageal reflex disease. This was thought to result from an accidental passage of massive insufflation of carbon dioxide gas across the diaphragm, leading to pneumomediastinum.

Predicting blood pressure change caused by rapid injection of propofol during anesthesia induction with a logistic regression model.

BACKGROUND: Propofol is a common intravenous agent for induction and maintenance of anesthesia. The advantage of propofol is rapid recovery of consciousness when the continuous infusion is stopped. Additionally, it has antiemetic effect of reducing postoperative nausea and vomiting. On the other hand, rapid infusion of propofol is painful and may cause hypotension. In this study, we aimed to develop a logistic regression model to accurately predict blood pressure change caused by rapid infusion of propofol. METHODS: Seventeen variables (including demographic data, past medical history, laboratory data, and blood pressure before induction) were assessed in 200 patients who received propofol for induction of anesthesia for routine surgery. A logistic regression model was derived using these values as independent variables to predict whether a patient would suffer a significant blood pressure change (> 30% decrease from baseline). Sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) were calculated to evaluate the performance of our prediction model. RESULTS: A cut-off value of 0.17 in the logistic regression model predicted decreased blood pressure with 90.0% sensitivity and, 67.3% specificity. The area under the receiver operating characteristic curve was 0.855. CONCLUSIONS: Our prediction model predicts propofol-induced hypotension with acceptable accuracy. Because of the straightforward mathematic formula used, our model can be integrated effortlessly into a hospital information system, providing a reliable and useful decision support for clinical anesthesia staff.