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Regional brain serotonin synthesis is increased in the olfactory bulbectomy rat model of depression: an autoradiographic study
Author(s) -
Watanabe Arata,
Tohyama Yoshihiro,
Nguyen Khanh Q.,
Hasegawa Shu,
Debonnel Guy,
Diksic Mirko
Publication year - 2003
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.2003.01702.x
Subject(s) - olfactory tubercle , dorsal raphe nucleus , medial forebrain bundle , ventral tegmental area , raphe nuclei , serotonin , medicine , neuroscience , endocrinology , limbic system , anterior olfactory nucleus , raphe , locus coeruleus , cingulate cortex , stria terminalis , olfactory bulb , hippocampus , biology , amygdala , central nervous system , dopamine , serotonergic , striatum , dopaminergic , receptor
Serotonin synthesis rates were evaluated using α‐[ 14 C]methyl‐ l ‐tryptophan (α‐MTrp) autoradiographic methods in olfactory bulbectomized (OBX) rats. They were significantly ( p < 0.05) increased in the frontal (50%) and parietal (40%) cortices, superior olive (over 30%), and the substantia nigra (30%) in the OBX rats as compared to the sham operated animals. There were also increases in 5‐hydroxytryptamine (5‐HT) synthesis in some limbic areas: the cingulate (32%), the medial forebrain bundle (58%), the hippocampus (13–25%) and the thalamus (22–40%). The largest increase in 5‐HT synthesis after OBX was observed in the sensory‐motor cortex (67%). 5‐HT synthesis rates were significantly decreased in the dorsal and medial raphe nuclei, but there was no significant change the ventral tegmental area and the locus coeruleus following OBX. These results indicate that olfactory bulbectomy causes an imbalance in 5‐HT synthesis in some projection areas by disproportionally increasing 5‐HT synthesis rates in specific brain regions and making more 5‐HT available for neurotransmission. This imbalance in 5‐HT synthesis and the subsequent elevation of tissue 5‐HT may be responsible for the creation of non‐physiological circuitry which may, in part, be reflected in the symptoms resembling human depression.