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Aging is a risk factor of human depression. Middle-aged or older men are vulnerable to adverse life events and an absence of social contact and easily become depressed. In the present study, we investigated the influence of aging on responses to life events in socially isolated conditions. We applied isolation-rearing (4 W) to two age groups, older (18 M)(More)
Isolation and acute environmental change are risk factors in human depression. In the present study, we investigated the differences in the brain monoamine activity of rats between two rearing conditions, isolated and group. Moreover, we examined the responses to novelty stress. Male F344 rats aged 11 weeks were divided into the above two groups. Four weeks(More)
Alteration of tryptophan (TRP) metabolism elicited by proinflammatory cytokines has gained attention as a new concept to explain the etiological and pathophysiological mechanisms of major depression. The kynurenine (KYN) pathway, which is initiated by indoleamine 2,3-dioxygenase (IDO), is the main TRP metabolic pathway. It shares TRP with the serotonin(More)
The kynurenine (KYN) pathway, which is initiated by indoleamine 2,3-dioxygenase, is the main tryptophan (TRP) metabolic pathway. It shares TRP with the serotonin (5-HT) pathway. We investigated the influence of inescapable-predator (rat) stress on behavior and brain TRP metabolism in mice. Male ICR mice (4W) were exposed to 20-min inescapable-predator(More)
The serious and characteristic side effects of interferon-alpha (IFN-alpha) therapy on the central nervous system, resulting in such problems as affective disorders or parkinsonism, have led us to investigate the biochemical mechanism of the effects of IFN-alpha on the monoaminergic neurotransmitter system using an animal model (rats). We first examined the(More)
The authors investigated the effects of fluvoxamine on neurochemical changes in the hippocampus elicited by isolation housing and novelty stress. Male F344 rats (11 w) were housed one per cage for four weeks. On each day of the last week (7 days) they were s.c. injected with fluvoxamine (20 mg/kg), and then subjected to novelty stress. Isolation housing(More)
Tetrahydrobiopterin (BH(4)) is a coenzyme of tyrosine hydroxylase (TH) and tryptophan hydroxylase (TPH), which are rate-limiting enzymes of monoamine biosynthesis. According to the monoamine hypothesis of depression, antidepressants will restore the function of the brain monoaminergic system and the BH(4) concentration. In the present study, we investigated(More)
In the present study, we investigated the effects of fluvoxamine, a selective serotonin reuptake inhibitor, on brain tetrahydrobiopterin (BH4) levels. We directly measured levels of BH4 by Tani and Ohno's direct method as well as the serotonin (5-HT) turnover ratio, i.e. 5-hydroxyindoleacetic acid (5-HIAA)/5-HT, after sub-acute s.c. injection of fluvoxamine(More)
RATIONALE Tetrahydrobiopterin (BH4) is a coenzyme of tyrosine hydroxylase (TH) and tryptophan hydroxylase (TPH), rate-limiting enzymes of monoamine biosynthesis. According to the monoamine hypothesis of depression, antidepressants will restore the function of the brain monoaminergic system, and BH4 concentration. OBJECTIVE To investigate the effects of(More)
The kynurenine (KYN) pathway, which is initiated by indoleamine 2,3-dioxygenase (IDO), is a tryptophan (TRP) metabolic pathway. It shares TRP with the serotonin (5-hydroxytryptamine, 5-HT) pathway. In major depression, activation of the KYN pathway may deplete 5-HT. In the present study we investigated the influence of various risk factors for depression,(More)