title: Monoamine oxidase inhibitors reduce conditioned fear stress-induced freezing behavior in rats.
abstract: The present study examined the acute anxiolytic effects of monoamine oxidase inhibitors on freezing behavior, a putative index of anxiety induced by conditioned fear stress. The selective serotonin 1A receptor agonist tandospirone (0.1-10 mg/kg) inhibited freezing dose dependently. The irreversible, non-selective monoamine oxidase inhibitors tranylcypromine (3 and 15 mg/kg) and phenelzine (30 and 80 mg/kg) reduced freezing significantly. Clorgyline (10 mg/kg, irreversible selective monoamine oxidase A inhibitor), N-(2-aminoethyl)-5-(m-fluorophenyl)-4-thiazole carboxamide (Ro 41-1049) (30 mg/kg, reversible selective monoamine oxidase A inhibitor), selegiline (3 mg/kg, irreversible selective monoamine oxidase B inhibitor) and lazabemide (10 mg/kg, reversible selective monoamine oxidase B inhibitor) had no effect on freezing behavior. However, combined administration of clorgyline (10 mg/kg) and selegiline (3 mg/kg) reduced freezing significantly, as well as combined administration of clorgyline (10 mg/kg) and lazabemide (10 mg/kg), Ro 41-1049 (30 mg/kg) and selegiline (3 mg/kg), or Ro 41-1049 (30 mg/kg) and lazabemide (10 mg/kg). These effects of monoamine oxidase inhibitors on freezing were not due to non-specific motor effects. These results suggest that acute inhibition of both monoamine oxidase A and B reduced anxiety or fear, while inhibition of monoamine oxidase A or B alone failed to reduce anxiety or fear.
authors.affiliation: Department of Psychiatry, Hokkaido University Graduate School of Medicine, North 15, West 7, Kita-ku, 060-8638, Sapporo, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Maki
authors.forename: T
authors.initials: T
authors.lastname: Inoue
authors.forename: T
authors.initials: T
authors.lastname: Izumi
authors.forename: I
authors.initials: I
authors.lastname: Muraki
authors.forename: K
authors.initials: K
authors.lastname: Ito
authors.forename: Y
authors.initials: Y
authors.lastname: Kitaichi
authors.forename: X
authors.initials: X
authors.lastname: Li
authors.forename: T
authors.initials: T
authors.lastname: Koyama
mesh_terms: D000818:Animals; D014151:Anti-Anxiety Agents / Q000494:pharmacology*; D001522:Behavior, Animal / Q000187:drug effects*; D004359:Drug Therapy, Combination; D005239:Fear; D008297:Male; D017551:Microdialysis; D008996:Monoamine Oxidase Inhibitors / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D014151:Anti-Anxiety Agents; D008996:Monoamine Oxidase Inhibitors