title: Primidone inhibits TRPM3 and attenuates thermal nociception in vivo.
abstract: The melastatin-related transient receptor potential (TRP) channel TRPM3 is a nonselective cation channel expressed in nociceptive neurons and activated by heat. Because TRPM3-deficient mice show inflammatory thermal hyperalgesia, pharmacological inhibition of TRPM3 may exert antinociceptive properties. Fluorometric Ca influx assays and a compound library containing approved or clinically tested drugs were used to identify TRPM3 inhibitors. Biophysical properties of channel inhibition were assessed using electrophysiological methods. The nonsteroidal anti-inflammatory drug diclofenac, the tetracyclic antidepressant maprotiline, and the anticonvulsant primidone were identified as highly efficient TRPM3 blockers with half-maximal inhibition at 0.6 to 6 μM and marked specificity for TRPM3. Most prominently, primidone was biologically active to suppress TRPM3 activation by pregnenolone sulfate (PregS) and heat at concentrations markedly lower than plasma concentrations commonly used in antiepileptic therapy. Primidone blocked PregS-induced Cai influx through TRPM3 by allosteric modulation and reversibly inhibited atypical inwardly rectifying TRPM3 currents induced by coapplication of PregS and clotrimazole. In vivo, analgesic effects of low doses of primidone were demonstrated in mice, applying PregS- and heat-induced pain models, including inflammatory hyperalgesia. Thus, applying the approved drug at concentrations that are lower than those needed to induce anticonvulsive effects offers a shortcut for studying physiological and pathophysiological roles of TRPM3 in vivo.
authors.affiliation: Rudolf-Boehm-Institut für Pharmakologie und Toxikologie, Universität Leipzig, Leipzig, Germany.
authors.forename: Ute
authors.initials: U
authors.lastname: Krügel
authors.affiliation: Rudolf-Boehm-Institut für Pharmakologie und Toxikologie, Universität Leipzig, Leipzig, Germany.|Carl-Ludwig-Institut für Physiologie, Universität Leipzig, Leipzig, Germany.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Straub
authors.affiliation: Rudolf-Boehm-Institut für Pharmakologie und Toxikologie, Universität Leipzig, Leipzig, Germany.
authors.forename: Holger
authors.initials: H
authors.lastname: Beckmann
authors.affiliation: Rudolf-Boehm-Institut für Pharmakologie und Toxikologie, Universität Leipzig, Leipzig, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Schaefer
mesh_terms: D018759:Adrenergic Uptake Inhibitors / Q000494:pharmacology / Q000627:therapeutic use; D000700:Analgesics / Q000494:pharmacology / Q000627:therapeutic use*; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology / Q000627:therapeutic use; D002118:Calcium / Q000378:metabolism; D004008:Diclofenac / Q000494:pharmacology; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D005727:Ganglia, Spinal / Q000166:cytology; D057809:HEK293 Cells; D006801:Humans; D006930:Hyperalgesia / Q000188:drug therapy* / Q000209:etiology; D008297:Male; D008376:Maprotiline / Q000494:pharmacology / Q000627:therapeutic use; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000187:drug effects; D010146:Pain / Q000139:chemically induced / Q000503:physiopathology*; D017288:Pain Threshold / Q000187:drug effects; D018408:Patch-Clamp Techniques; D011284:Pregnenolone / Q000633:toxicity*; D011324:Primidone / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use*; D051381:Rats; D050053:TRPM Cation Channels / Q000378:metabolism*
chemical_list: D018759:Adrenergic Uptake Inhibitors; D000700:Analgesics; D000894:Anti-Inflammatory Agents, Non-Steroidal; D050053:TRPM Cation Channels; C533868:TRPM3 protein, mouse; D011324:Primidone; D004008:Diclofenac; D008376:Maprotiline; D011284:Pregnenolone; D002118:Calcium