Effects of conditioned fear stress on 5-HT release in the rat prefrontal cortex.
The effects of conditioned fear stress (CFS) on 5-HT release in the medial prefrontal cortex were studied by in vivo microdialysis. CFS (exposure to an environment in which foot-shock had been delivered previously) induced a marked suppression of motility-that is, freezing behavior. The extracellular concentration of 5-HT in the medial prefrontal cortex increased during this freezing behavior, but no significant changes were observed in the concentration of its metabolite, 5-HIAA. The increased 5-HT concentration returned to pretreatment levels when the animals were returned to their home cages. Diazepam (0.5 mg/kg, intraperitoneally) reduced the CFS-induced freezing behavior and prevented the increases in extracellular 5-HT levels. A 5-HT3 receptor antagonist, tropisetron (10 and 100 micrograms/kg), also inhibited both the CFS-induced increase in 5-HT release and the freezing behavior. These findings suggest that there is a relationship between anxiety and 5-HT release in the prefrontal cortex and that the 5-HT3 receptor antagonist tropisetron might have anxiolytic properties.
Yoshioka
M
M
First Department of Pharmacology, Hokkaido University School of Medicine, Sapporo, Japan.
Matsumoto
M
M
Togashi
H
H
Saito
H
H
D000818:Animals; D003213:Conditioning, Psychological / Q000502:physiology*; D003975:Diazepam / Q000494:pharmacology; D005239:Fear / Q000502:physiology*; D007211:Indoles / Q000494:pharmacology; D008297:Male; D017551:Microdialysis; D017397:Prefrontal Cortex / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000378:metabolism*; D012702:Serotonin Antagonists / Q000494:pharmacology; D013315:Stress, Psychological / Q000378:metabolism*; D000077526:Tropisetron
D007211:Indoles; D012702:Serotonin Antagonists; D012701:Serotonin; D000077526:Tropisetron; D003975:Diazepam