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McKinstry-Wu AR, Wasilczuk AZ, Dailey WP, Eckenhoff RG, Kelz MB. In Vivo Photoadduction of Anesthetic Ligands in Mouse Brain Markedly Extends Sedation and Hypnosis. J Neurosci 2023; 43:2338-2348. [PMID: 36849414 PMCID: PMC10072292 DOI: 10.1523/jneurosci.1884-22.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 02/16/2023] [Accepted: 02/17/2023] [Indexed: 03/01/2023] Open
Abstract
Photoaffinity ligands are best known as tools used to identify the specific binding sites of drugs to their molecular targets. However, photoaffinity ligands have the potential to further define critical neuroanatomic targets of drug action. In the brains of WT male mice, we demonstrate the feasibility of using photoaffinity ligands in vivo to prolong anesthesia via targeted yet spatially restricted photoadduction of azi-m-propofol (aziPm), a photoreactive analog of the general anesthetic propofol. Systemic administration of aziPm with bilateral near-ultraviolet photoadduction in the rostral pons, at the border of the parabrachial nucleus and locus coeruleus, produced a 20-fold increase in the duration of sedative and hypnotic effects compared with control mice without UV illumination. Photoadduction that missed the parabrachial-coerulean complex also failed to extend the sedative or hypnotic actions of aziPm and was indistinguishable from nonadducted controls. Paralleling the prolonged behavioral and EEG consequences of on target in vivo photoadduction, we conducted electrophysiologic recordings in rostral pontine brain slices. Using neurons within the locus coeruleus to further highlight the cellular consequences of irreversible aziPm binding, we demonstrate transient slowing of spontaneous action potentials with a brief bath application of aziPm that becomes irreversible on photoadduction. Together, these findings suggest that photochemistry-based strategies are a viable new approach for probing CNS physiology and pathophysiology.SIGNIFICANCE STATEMENT Photoaffinity ligands are drugs capable of light-induced irreversible binding, which have unexploited potential to identify the neuroanatomic sites of drug action. We systemically administer a centrally acting anesthetic photoaffinity ligand in mice, conduct localized photoillumination within the brain to covalently adduct the drug at its in vivo sites of action, and successfully enrich irreversible drug binding within a restricted 250 µm radius. When photoadduction encompassed the pontine parabrachial-coerulean complex, anesthetic sedation and hypnosis was prolonged 20-fold, thus illustrating the power of in vivo photochemistry to help unravel neuronal mechanisms of drug action.
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Affiliation(s)
- Andrew R McKinstry-Wu
- Department of Anesthesiology and Critical Care, University of Pennsylvania Perelman School of Medicine, Philadelphia, Philadelphia 19104
- Neuroscience of Unconsciousness and Reanimation Research Alliance, University of Pennsylvania, Perelman School of Medicine, Philadelphia, Philadelphia 19104
| | - Andrzej Z Wasilczuk
- Department of Anesthesiology and Critical Care, University of Pennsylvania Perelman School of Medicine, Philadelphia, Philadelphia 19104
- Department of Bioengineering, University of Pennsylvania, Philadelphia, Philadelphia 19104
- Neuroscience of Unconsciousness and Reanimation Research Alliance, University of Pennsylvania, Perelman School of Medicine, Philadelphia, Philadelphia 19104
| | - William P Dailey
- Department of Chemistry, University of Pennsylvania School of Arts and Sciences, Philadelphia, Pennsylvania 19104
| | - Roderic G Eckenhoff
- Department of Anesthesiology and Critical Care, University of Pennsylvania Perelman School of Medicine, Philadelphia, Philadelphia 19104
| | - Max B Kelz
- Department of Anesthesiology and Critical Care, University of Pennsylvania Perelman School of Medicine, Philadelphia, Philadelphia 19104
- Mahoney Institute for Neurosciences, University of Pennsylvania, Perelman School of Medicine, Philadelphia, Philadelphia 19104
- Neuroscience of Unconsciousness and Reanimation Research Alliance, University of Pennsylvania, Perelman School of Medicine, Philadelphia, Philadelphia 19104
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McKinstry-Wu AR, Woll KA, Joseph TT, Bu W, White ER, Bhanu NV, Garcia BA, Brannigan G, Dailey WP, Eckenhoff RG. Azi-medetomidine: Synthesis and Characterization of a Novel α2 Adrenergic Photoaffinity Ligand. ACS Chem Neurosci 2019; 10:4716-4728. [PMID: 31638765 DOI: 10.1021/acschemneuro.9b00484] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Agonists at the α2 adrenergic receptor produce sedation, increase focus, provide analgesia, and induce centrally mediated hypotension and bradycardia, yet neither their dynamic interactions with adrenergic receptors nor their modulation of neuronal circuit activity is completely understood. Photoaffinity ligands of α2 adrenergic agonists have the potential both to capture discrete moments of ligand-receptor interactions and to prolong naturalistic drug effects in discrete regions of tissue in vivo. We present here the synthesis and characterization of a novel α2 adrenergic agonist photolabel based on the imidazole medetomidine called azi-medetomidine. Azi-medetomidine shares protein association characteristics with its parent compound in experimental model systems and by molecular dynamics simulation of interactions with the α2A adrenergic receptor. Azi-medetomidine acts as an agonist at α2A adrenergic receptors, and produces hypnosis in Xenopus laevis tadpoles. Azi-medetomidine competes with the α2 agonist clonidine at α2A adrenergic receptors, which is potentiated by photolabeling, and azi-medetomidine labels moieties on the α2A adrenergic receptor as determined by mass spectrometry in a manner consistent with a simulated model. This novel α2 adrenergic agonist photolabel can serve as a powerful tool for in vitro and in vivo investigations of adrenergic signaling.
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Affiliation(s)
- Andrew R. McKinstry-Wu
- Department of Anesthesiology & Critical Care, University of Pennsylvania Perelman School of Medicine, 3620 Hamilton Walk, Philadelphia, Pennsylvania 19104, United States
| | - Kellie A. Woll
- Department of Anesthesiology & Critical Care, University of Pennsylvania Perelman School of Medicine, 3620 Hamilton Walk, Philadelphia, Pennsylvania 19104, United States
| | - Thomas T. Joseph
- Department of Anesthesiology & Critical Care, University of Pennsylvania Perelman School of Medicine, 3620 Hamilton Walk, Philadelphia, Pennsylvania 19104, United States
| | - Weiming Bu
- Department of Anesthesiology & Critical Care, University of Pennsylvania Perelman School of Medicine, 3620 Hamilton Walk, Philadelphia, Pennsylvania 19104, United States
| | - E. Railey White
- Department of Anesthesiology & Critical Care, University of Pennsylvania Perelman School of Medicine, 3620 Hamilton Walk, Philadelphia, Pennsylvania 19104, United States
| | - Natarajan V. Bhanu
- Epigenetics Institute, Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Benjamin A. Garcia
- Epigenetics Institute, Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Grace Brannigan
- Center for Computational and Integrative Biology, Department of Physics, Rutgers University, Camden, New Jersey 08102, United States
| | - William P. Dailey
- Department of Chemistry, University of Pennsylvania School of Arts and Sciences, 231 S. 34th Street, Philadelphia, Pennsylvania 19104, United States
| | - Roderic G. Eckenhoff
- Department of Anesthesiology & Critical Care, University of Pennsylvania Perelman School of Medicine, 3620 Hamilton Walk, Philadelphia, Pennsylvania 19104, United States
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