Effect of conditioned fear stress on serotonin metabolism in the rat brain.
The effects of electric foot-shock stress (EFS) and conditioned fear stress (CFS) on serotonin [5-hydroxytryptamine (5-HT)] metabolism in seven various brain regions of the rat were studied by measuring tryptophan, 5-HT and 5-hydroxyindoleacetic acid (5-HIAA). EFS for 30 min increased tryptophan levels in almost all brain regions but did not change 5-HT levels in any regions. It increased 5-HIAA levels in the medial prefrontal cortex (mPFC), nucleus accumbens, and amygdala. CFS (exposure to an environment paired previously with foot-shock) increased defecation and induced freezing behavior. It failed to change tryptophan and 5-HT levels in any brain regions but increased 5-HIAA level only in the mPFC. In contrast to EFS, which increased 5-HT metabolism in several other brain regions, increased metabolism of 5-HT was especially marked in the mPFC after CFS, regarded as psychological stress.
Inoue
T
T
Department of Psychiatry and Neurology, Hokkaido University School of Medicine, Sapporo, Japan.
Koyama
T
T
Yamashita
I
I
D000818:Animals; D001921:Brain / Q000378:metabolism*; D003214:Conditioning, Classical / Q000502:physiology*; D003672:Defecation / Q000502:physiology; D004597:Electroshock; D005239:Fear / Q000502:physiology*; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D008297:Male; D009043:Motor Activity / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000378:metabolism*; D013312:Stress, Physiological / Q000378:metabolism*; D014364:Tryptophan / Q000378:metabolism
D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D014364:Tryptophan