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Cobo R, Nikolaeva M, Alberola-Die A, Fernández-Ballester G, González-Ros JM, Ivorra I, Morales A. Mechanisms Underlying the Strong Inhibition of Muscle-Type Nicotinic Receptors by Tetracaine. Front Mol Neurosci 2018; 11:193. [PMID: 30135641 PMCID: PMC6092513 DOI: 10.3389/fnmol.2018.00193] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Accepted: 05/15/2018] [Indexed: 11/13/2022] Open
Abstract
Nicotinic acetylcholine (ACh) receptors (nAChRs) are included among the targets of a variety of local anesthetics, although the molecular mechanisms of blockade are still poorly understood. Some local anesthetics, such as lidocaine, act on nAChRs by different means through their ability to present as both charged and uncharged molecules. Thus, we explored the mechanisms of nAChR blockade by tetracaine, which at physiological pH is almost exclusively present as a positively charged local anesthetic. The nAChRs from Torpedo electroplaques were transplanted to Xenopus oocytes and the currents elicited by ACh (IACh s), either alone or co-applied with tetracaine, were recorded. Tetracaine reversibly blocked IACh , with an IC50 (i.e., the concentration required to inhibit half the maximum IACh ) in the submicromolar range. Notably, at very low concentrations (0.1 μM), tetracaine reduced IACh in a voltage-dependent manner, the more negative potentials produced greater inhibition, indicating open-channel blockade. When the tetracaine concentration was increased to 0.7 μM or above, voltage-independent inhibition was also observed, indicating closed-channel blockade. The IACh inhibition by pre-application of just 0.7 μM tetracaine before superfusion of ACh also corroborated the notion of tetracaine blockade of resting nAChRs. Furthermore, tetracaine markedly increased nAChR desensitization, mainly at concentrations equal or higher than 0.5 μM. Interestingly, tetracaine did not modify desensitization when its binding within the channel pore was prevented by holding the membrane at positive potentials. Tetracaine-nAChR interactions were assessed by virtual docking assays, using nAChR models in the closed and open states. These assays revealed that tetracaine binds at different sites of the nAChR located at the extracellular and transmembrane domains, in both open and closed conformations. Extracellular binding sites seem to be associated with closed-channel blockade; whereas two sites within the pore, with different affinities for tetracaine, contribute to open-channel blockade and the enhancement of desensitization, respectively. These results demonstrate a concentration-dependent heterogeneity of tetracaine actions on nAChRs, and contribute to a better understanding of the complex modulation of muscle-type nAChRs by local anesthetics. Furthermore, the combination of functional and virtual assays to decipher nAChR-tetracaine interactions has allowed us to tentatively assign the main nAChR residues involved in these modulating actions.
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Affiliation(s)
- Raúl Cobo
- División de Fisiología, Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Alicante, Spain
| | - Magdalena Nikolaeva
- Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, Alicante, Spain
| | - Armando Alberola-Die
- División de Fisiología, Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Alicante, Spain
| | | | - José M González-Ros
- Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, Alicante, Spain
| | - Isabel Ivorra
- División de Fisiología, Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Alicante, Spain
| | - Andrés Morales
- División de Fisiología, Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Alicante, Spain
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Emelife PI, Eng MR, Menard BL, Myers AS, Cornett EM, Urman RD, Kaye AD. Adjunct medications for peripheral and neuraxial anesthesia. Best Pract Res Clin Anaesthesiol 2018; 32:83-99. [PMID: 30322466 DOI: 10.1016/j.bpa.2018.06.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 06/18/2018] [Indexed: 02/06/2023]
Abstract
Regional and neuraxial anesthesia can provide a safer perioperative experience, greater satisfaction, reduced opioid consumption, and reduction of pain, while minimizing side effects. Ultrasound technology has aided clinicians in depositing local anesthetic medication in precise proximity to targeted peripheral nerves. There are a plethora of adjuvants that have been utilized to prolong local anesthetic actions and enhance effects in peripheral nerve blocks. This manuscript describes the current state of the use of adjuncts, e.g., dexmedetomidine, dexamethasone, clonidine, epinephrine, etc., in regional anesthesia. Additionally, evidence behind dosing and block prolongation is summarized along with patient outcomes, adverse effects, and future directions.
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Affiliation(s)
- Patrick Ifesinachi Emelife
- Department of Anesthesiology, LSU Health Sciences Center, Room 653, 1542 Tulane Ave., New Orleans, LA, 70112, USA.
| | - Matthew R Eng
- Department of Anesthesiology, LSU Health Sciences Center, Room 656, 1542 Tulane Ave., New Orleans, LA, 70112, USA.
| | - Bethany L Menard
- Department of Anesthesiology, LSU Health Sciences Center, Room 656, 1542 Tulane Ave., New Orleans, LA, 70112, USA.
| | - Andrew S Myers
- LSU Health Sciences Center, 433 Bolivar St., New Orleans, LA, 70112, USA.
| | - Elyse M Cornett
- Department of Anesthesiology, LSU Health Shreveport, 1501 Kings Highway, Shreveport, LA, 71103, USA.
| | - Richard D Urman
- Department of Anesthesiology, Perioperative and Pain Medicine, Harvard Medical School, Brigham and Women's Hospital, 75 Francis St, Boston, MA, 02115, USA.
| | - Alan D Kaye
- Department of Anesthesiology, LSU Health Sciences Center, Room 653, 1542 Tulane Ave., New Orleans, LA, 70112, USA.
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Swain A, Nag DS, Sahu S, Samaddar DP. Adjuvants to local anesthetics: Current understanding and future trends. World J Clin Cases 2017; 5:307-323. [PMID: 28868303 PMCID: PMC5561500 DOI: 10.12998/wjcc.v5.i8.307] [Citation(s) in RCA: 106] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2017] [Revised: 05/03/2017] [Accepted: 05/19/2017] [Indexed: 02/05/2023] Open
Abstract
Although beneficial in acute and chronic pain management, the use of local anaesthetics is limited by its duration of action and the dose dependent adverse effects on the cardiac and central nervous system. Adjuvants or additives are often used with local anaesthetics for its synergistic effect by prolonging the duration of sensory-motor block and limiting the cumulative dose requirement of local anaesthetics. The armamentarium of local anesthetic adjuvants have evolved over time from classical opioids to a wide array of drugs spanning several groups and varying mechanisms of action. A large array of opioids ranging from morphine, fentanyl and sufentanyl to hydromorphone, buprenorphine and tramadol has been used with varying success. However, their use has been limited by their adverse effect like respiratory depression, nausea, vomiting and pruritus, especially with its neuraxial use. Epinephrine potentiates the local anesthetics by its antinociceptive properties mediated by alpha-2 adrenoreceptor activation along with its vasoconstrictive properties limiting the systemic absorption of local anesthetics. Alpha 2 adrenoreceptor antagonists like clonidine and dexmedetomidine are one of the most widely used class of local anesthetic adjuvants. Other drugs like steroids (dexamethasone), anti-inflammatory agents (parecoxib and lornoxicam), midazolam, ketamine, magnesium sulfate and neostigmine have also been used with mixed success. The concern regarding the safety profile of these adjuvants is due to its potential neurotoxicity and neurological complications which necessitate further research in this direction. Current research is directed towards a search for agents and techniques which would prolong local anaesthetic action without its deleterious effects. This includes novel approaches like use of charged molecules to produce local anaesthetic action (tonicaine and n butyl tetracaine), new age delivery mechanisms for prolonged bioavailability (liposomal, microspheres and cyclodextrin systems) and further studies with other drugs (adenosine, neuromuscular blockers, dextrans).
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Diabetic-induced increased sodium channel activity attenuated by tetracaine in sensory neurons in vitro. Biochem Biophys Res Commun 2014; 453:296-301. [DOI: 10.1016/j.bbrc.2014.09.035] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Accepted: 09/09/2014] [Indexed: 11/22/2022]
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Leng T, Lin J, Cottrell JE, Xiong ZG. Subunit and frequency-dependent inhibition of acid sensing ion channels by local anesthetic tetracaine. Mol Pain 2013; 9:27. [PMID: 23758830 PMCID: PMC3695766 DOI: 10.1186/1744-8069-9-27] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Accepted: 06/05/2013] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Extracellular acidosis is a prominent feature of multiple pathological conditions, correlating with pain sensation. Acid-sensing ion channels (ASICs), a family of proton-gated cation channels, are distributed throughout the central and peripheral nervous systems. Activation of ASICs, particularly ASIC3 and ASIC1a channels, by acidic pH and the resultant depolarization of nociceptive primary sensory neurons, participates in nociception. Agents that inhibit the activation of ASICs are thus expected to be analgesic. Here, we studied the effect of local anesthetic tetracaine on ASIC currents. RESULTS Tetracaine inhibited the peak ASIC3 current in a concentration-dependent manner with an IC50 of 9.96 ± 1.88 mM. The degree of inhibition by tetracaine was dependent on the extracellular pH but independent of the membrane potential. Furthermore, 3 mM tetracaine also inhibited 29.83% of the sustained ASIC3 current. In addition to ASIC3, tetracaine inhibited the ASIC1a and ASIC1β currents. The inhibition of the ASIC1a current was influenced by the frequency of channel activation. In contrast to ASIC3, ASIC1a, and ASIC1β currents, ASIC2a current was not inhibited by tetracaine. In cultured mouse dorsal root ganglion neurons, 1-3 mM tetracaine inhibited both the transient and sustained ASIC currents. At pH4.5, 3 mM tetracaine reduced the peak ASIC current to 60.06 ± 4.51%, and the sustained current to 48.24 ± 7.02% of the control values in dorsal root ganglion neurons. In contrast to ASICs, voltage-gated sodium channels were inhibited by acid, with 55.15% inhibition at pH6.0 and complete inhibition at pH5.0. CONCLUSIONS These findings disclose a potential new mechanism underlying the analgesic effects of local anesthetics, particularly in acidic conditions where their primary target (i.e. voltage-gated Na+ channel) has been suppressed by protons.
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Kissin I, Freitas CF, Mulhern HL, DeGirolami U. Sciatic nerve block with resiniferatoxin: an electron microscopic study of unmyelinated fibers in the rat. Anesth Analg 2007; 105:825-31. [PMID: 17717246 DOI: 10.1213/01.ane.0000277491.40055.47] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
BACKGROUND Perineural administration of the naturally occurring vanilloids (capsaicin, resiniferatoxin [RTX]) produces selective nociceptive blockade. Studies using perineural vanilloids in high concentrations suggest that they can cause a degeneration of unmyelinated fibers. However, electron microscopic studies of local vanilloid toxicity produced conflicting outcomes. In the present study, we sought to determine whether RTX-induced reversible sciatic nerve block results in the degenerative changes of unmyelinated fibers. METHODS In rat experiments, RTX was administered percutaneously at the sciatic nerve. The effect of RTX was monitored by measuring the rat's response to noxious heat. The sciatic nerves were removed 48 h after the blockade initiation. Quantitative electron microscopic evaluation of the unmyelinated fibers was performed in three groups of animals: RTX 0.0001% (0.1 microg), RTX 0.001% (1 microg), and control (RTX vehicle, 0.1 mL). RESULTS Cross-sections of the sciatic nerve 48 h after the initiation of RTX-induced reversible nerve blockade appeared essentially normal. One rarely observed finding was the irregularly compacted membranous deposits in the unmyelinated axons. The frequency of this finding was approximately one per thousand fibers with both concentrations of RTX. CONCLUSIONS The results of the study suggest that a selective and long-lasting sciatic nerve block (up to 2 wk) can be provided by RTX without any significant damage to the unmyelinated nerve fibers.
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Affiliation(s)
- Igor Kissin
- Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA.
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Kissin I, Davison N, Bradley EL. Perineural resiniferatoxin prevents hyperalgesia in a rat model of postoperative pain. Anesth Analg 2005; 100:774-780. [PMID: 15728067 DOI: 10.1213/01.ane.0000143570.75908.7f] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Resiniferatoxin (RTX) is a vanilloid agonist with a unique spectrum of activities. Vanilloids bind to the transient receptor potential ion channel subtype 1, a nonselective cation ionophore important in the integration of different noxious signals. Vanilloid agonists selectively decrease sensitivity to noxious stimuli. In this study, we sought to determine whether perineural RTX prevents hyperalgesia in a model of incisional pain. In a rat model, RTX was administered percutaneously to the sciatic and saphenous nerves before the plantar incision. The withdrawal response to von Frey filaments, the struggle response to pressure on the paw, and pain scoring based on weight bearing were measured before RTX and at various intervals for 8 days after RTX. A percutaneous injection of RTX (0.0003%) to the sciatic (0.1 mL) and saphenous (0.05 mL) nerves completely prevented incisional hyperalgesia. Two hours after incision, the withdrawal threshold was 51 mN without and 456 mN with RTX (P < 0.0001). RTX also prevented the incision-induced decrease in struggle threshold and abolished the pain behavior associated with weight bearing. We conclude that RTX provides a type of neural blockade when postoperative pain is abolished and that nonpainful sensations and motor functions are preserved.
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Affiliation(s)
- Igor Kissin
- *Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts; and †Department of Biostatistics, University of Alabama at Birmingham
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McCarthy RJ, Kerns JM, Nath HA, Shulman M, Ivankovich AD. The antinociceptive and histologic effect of sciatic nerve blocks with 5% butamben suspension in rats. Anesth Analg 2002; 94:711-6; table of contents. [PMID: 11867403 DOI: 10.1097/00000539-200203000-00043] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
UNLABELLED Butamben, a lipophilic local anesthetic of the ester class, produces a differential nerve block of long duration. Epidural and peripheral nerve blocks with butamben, formulated as a 5%--10% suspension, result in prolonged analgesia without significant motor blockade. We evaluated the effect of butamben sciatic nerve block on antinociception using the rat paw formalin test, as well as withdrawal latencies to thermal stimulation, and assessed histologic changes in the nerve. After right sciatic nerve block with butamben 5% or saline, responses to intradermal injection of 5% formalin were recorded in randomly selected groups of 6 animals each on days 1, 2, 5, 10, 21, and 28. In an additional group of 8 thermal challenges to both hind paws were recorded at 1, 2, 5, 7, 10, 14, 17, 21, and 28 days after right sciatic butamben 5% blocks. Butamben injection decreased the formalin-induced flinches on days 2, 5, 10, 21 and 28 and decreased thermal challenges on days 1 through 17. Histologic changes were minimal. This study demonstrates a prolonged antinociceptive effect from butamben nerve block to both formalin-induced nociception and heat hyperalgesia, without an effect on gross motor function or histologic morphology. IMPLICATIONS Butamben 5% nerve blocks produced a prolonged antinociceptive effect to formalin-induced nociception and heat hyperalgesia, without significant motor effect or evidence of substantial histologic changes.
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Affiliation(s)
- Robert J McCarthy
- Departments of Anesthesiology and Anatomy, Rush Medical College at Rush-Presbyterian-St. Luke's Medical Center, Chicago, Illinois 60611, USA.
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Kissin I, Lee SS, Bradley EL. Hyperalgesia Caused by Nerve Transection: Long-Lasting Block Prevents Early Hyperalgesia in the Receptive Field of the Surviving Nerve. Anesth Analg 1999. [DOI: 10.1213/00000539-199912000-00030] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Lázaro JJ, Franquelo C, Navarro X, Castellano B, Verdú E, Cristòfol C, Arboix M. Prolongation of nerve and epidural anesthetic blockade by bupivacaine in a lipid emulsion. Anesth Analg 1999; 89:121-7. [PMID: 10389789 DOI: 10.1097/00000539-199907000-00021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
UNLABELLED We assessed the effect of a lipid emulsion of bupivacaine on prolonging peripheral nerve and epidural anesthetic blockade in the rat. The intensity and duration of motor and sensory blockade produced by a single injection of aqueous solution (BPV-as) and lipid emulsion (BPV-em) preparations of 0.5% bupivacaine were evaluated by electrophysiological methods. Both preparations induced complete, reversible motor and sensory blockade after injection. The latency time to the maximal blockade and the duration of anesthetic blockade were more prolonged for BPV-em than for BPV-as. The increase in duration of maximal blockade was 1.4 times for nerve and 1.3 times for epidural anesthesia. Histological evaluation of spinal roots and spinal cord sections did not show any abnormalities or differences between animals injected with BPV-as and those injected with BPV-em. Pharmacokinetic studies showed lower plasma peak concentration and a longer elimination half-life for BPV-em than for BPV-as. Thus, BPV-em prolongs the effects of local anesthetics, allows a similar degree of blockade, and reduces the systems toxic effects of anesthetics compared with BPV-as. IMPLICATIONS We assessed a lipid emulsion containing bupivacaine for peripheral nerve and epidural anesthetic blockade in the rat. The emulsion allowed a complete blockade, while increasing the duration of the anesthetic effect (by 30%-40%), compared with the standard bupivacaine aqueous solution.
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Affiliation(s)
- J J Lázaro
- Department of Cell Biology and Physiology, Universitat Autònoma de Barcelona, Bellaterra, Spain
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