title: Effects of conditioned fear stress on serotonin neurotransmission and freezing behavior in rats.
abstract: In an attempt to clarify the role of the brain serotonergic system in the psychopathology of anxiety, we examined the effect of a psychological stress, conditioned fear stress, on extracellular serotonin (5-hydroxytryptamine, 5-HT) concentrations in the rat medial prefrontal cortex using the method of in vivo microdialysis, while simultaneously observing conditioned fear stress-induced freezing behavior, an index of anxiety. Conditioned fear stress increased extracellular 5-HT levels in the medial prefrontal cortex, and this 5-HT level increase was followed by a resolution of the freezing behavior. A dose of 10 mg/kg of a selective 5-HT reuptake inhibitor, citalopram, administered 60 min before exposure to conditioned fear stress increased extracellular 5-HT concentrations immediately and potently, reducing freezing behavior. These findings strongly suggest that facilitation of brain 5-HT neurotransmission decreases anxiety, which is in agreement with the clinical reports that selective 5-HT reuptake inhibitors are effective in the treatment of anxiety disorders.
authors.affiliation: Department of Psychiatry, Hokkaido University School of Medicine, Sapporo, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Hashimoto
authors.forename: T
authors.initials: T
authors.lastname: Inoue
authors.forename: T
authors.initials: T
authors.lastname: Koyama
mesh_terms: D000818:Animals; D001007:Anxiety / Q000378:metabolism / Q000523:psychology; D001522:Behavior, Animal / Q000187:drug effects; D015283:Citalopram / Q000494:pharmacology; D003213:Conditioning, Psychological; D005239:Fear / Q000523:psychology*; D008297:Male; D017551:Microdialysis; D017397:Prefrontal Cortex / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000378:metabolism*; D017367:Selective Serotonin Reuptake Inhibitors / Q000494:pharmacology; D013312:Stress, Physiological / Q000378:metabolism* / Q000523:psychology; D009435:Synaptic Transmission / Q000187:drug effects
chemical_list: D015283:Citalopram; D012701:Serotonin; D017367:Selective Serotonin Reuptake Inhibitors