[From a standpoint of psychiatry: effects of conditioned fear stress on monoaminergic systems in the rat brain].
The effects of electric footshock stress(EFS) and conditioned fear stress(CFS) on dopamine(DA) and serotonin(5-HT) metabolism in seven various brain regions of the rat were studied by measuring dihydroxyphenylacetic acid(DOPAC), homovanillic acid(HVA) and 5-hydroxyindoleacetic acid(5-HIAA). EFS for 30 min increased DOPAC and HVA levels in all seven brain regions and increased 5-HIAA levels in the medial prefrontal cortex(mPFC), nucleus accumbens and amygdala. CFS(exposure to an environment paired previously with footshock) increased plasma corticosterone levels and defecation, and induced freezing behavior. It also increased DOPAC levels in the mPFC, paraventricular nucleus of the hypothalamus and lateral hypothalamus, increased HVA levels in the mPFC and amygdala, and increased the 5-HIAA level in the mPFC. In contrast to EFS, which increased DA and 5-HT metabolism in several other brain regions, increased metabolism of both DA and 5-HT was especially marked in the mPFC after CFS. In this model, two classes of anxiolytics were examined for effects on freezing behavior. The benzodiazepine diazepam, a classical anxiolytic, reduced the freezing response. The new anxiolytic ipsapirone, a selective 5-HT1A agonist, also reduced the freezing response. These findings suggest the usefulness of this model for detecting the anxiolytic potential of drugs and examining the relation between 5-HT and anxiety.
Inoue
T
T
Department of Psychiatry and Neurology, Hokkaido University School of Medicine, Sapporo.
Koyama
T
T
Yamashita
I
I
D000818:Animals; D014151:Anti-Anxiety Agents / Q000494:pharmacology; D001923:Brain Chemistry; D004298:Dopamine / Q000378:metabolism*; D005239:Fear; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000378:metabolism*; D013315:Stress, Psychological / Q000378:metabolism*
D014151:Anti-Anxiety Agents; D012701:Serotonin; D004298:Dopamine