title: A Clickable Analogue of Ketamine Retains NMDA Receptor Activity, Psychoactivity, and Accumulates in Neurons.
abstract: Ketamine is a psychotomimetic and antidepressant drug. Although antagonism of cell-surface NMDA receptors (NMDARs) may trigger ketamine's psychoactive effects, ketamine or its major metabolite norketamine could act intracellularly to produce some behavioral effects. To explore the viability of this latter hypothesis, we examined intracellular accumulation of novel visualizable analogues of ketamine/norketamine. We introduced an alkyne "click" handle into norketamine (alkyne-norketamine, A-NK) at the key nitrogen atom. Ketamine, norketamine, and A-NK, but not A-NK-amide, showed acute and persisting psychoactive effects in mice. This psychoactivity profile paralleled activity of the compounds as NMDAR channel blockers; A-NK-amide was inactive at NMDARs, and norketamine and A-NK were active but ~4-fold less potent than ketamine. We incubated rat hippocampal cells with 10 μM A-NK or A-NK-amide then performed Cu2+catalyzed cycloaddition of azide-Alexa Fluor 488, which covalently attaches the fluorophore to the alkyne moiety in the compounds. Fluorescent imaging revealed intracellular localization of A-NK but weak A-NK-amide labeling. Accumulation was not dependent on membrane potential, NMDAR expression, or NMDAR activity. Overall, the approach revealed a correlation among NMDAR activity, intracellular accumulation/retention, and behavioral effects. Thus, we advance first generation chemical biology tools to aid in the identification of ketamine targets.
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110, USA.|Graduate Program in Neurosciences, Division of Biology and Biomedical Sciences, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110, USA.
authors.forename: Christine
authors.initials: C
authors.lastname: Emnett
authors.affiliation: Department of Radiology, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110, USA.
authors.forename: Hairong
authors.initials: H
authors.lastname: Li
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110, USA.
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Jiang
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110, USA.
authors.forename: Ann
authors.initials: A
authors.lastname: Benz
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110, USA.
authors.forename: Joseph
authors.initials: J
authors.lastname: Boggiano
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110, USA.
authors.forename: Sara
authors.initials: S
authors.lastname: Conyers
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110, USA.|Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110, USA.
authors.forename: David F
authors.initials: DF
authors.lastname: Wozniak
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110, USA.|Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110, USA.|Department of Neuroscience, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110, USA.
authors.forename: Charles F
authors.initials: CF
authors.lastname: Zorumski
authors.affiliation: Department of Radiology, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110, USA.|Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110, USA.
authors.forename: David E
authors.initials: DE
authors.lastname: Reichert
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110, USA.|Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110, USA.|Department of Neuroscience, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110, USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Mennerick
mesh_terms: D000818:Animals; D000928:Antidepressive Agents / Q000493:pharmacokinetics / Q000494:pharmacology; D001522:Behavior, Animal / Q000187:drug effects*; D057930:Click Chemistry; D007649:Ketamine / Q000031:analogs & derivatives / Q000493:pharmacokinetics / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects*; D051379:Mice; D009474:Neurons / Q000378:metabolism*; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D000928:Antidepressive Agents; D016194:Receptors, N-Methyl-D-Aspartate; D007649:Ketamine