[3H]paroxetine binding and serotonin content of rat cortical areas, hippocampus, neostriatum, ventral mesencephalic tegmentum, and midbrain raphe nuclei region following p-chlorophenylalanine and p-chloroamphetamine treatment.
The agents p-chlorophenylalanine (PCPA) and p-chloroamphetamine (PCA) deplete brain serotonin (5-HT) levels by two different mechanisms; PCPA inhibits the enzyme tryptophan hydroxylase, whereas PCA has a neurotoxic action on certain 5-HT neurons. The parameters of [3H]paroxetine binding to homogenates prepared from the cerebral cortex of rats treated with PCPA, PCA, or saline; vehicle were investigated. The tissue concentrations of 5-HT and 5-hydroxyindole-3-acetic acid (5-HIAA) were also determined by HPLC in the same brain samples. After PCPA treatment, neither the maximum binding capacity (Bmax) nor the dissociation constant (KD) of [3H]paroxetine for the 5-HT uptake recognition site differed from controls despite a substantial reduction in the concentration of 5-HT and 5-HIAA. In contrast, significant changes in both the Bmax and KD values were observed in the cerebral cortex of rats treated with PCA. Furthermore, [3H]paroxetine binding and tissue concentrations of 5-HT and 5-HIAA were measured in the following different regions of the rat brain: cingulate, parietal, and visual cortical areas; dorsal and ventral hippocampus; rostral and caudal halves of neostriatum; ventral mesencephalic tegmentum; and midbrain raphe nuclei region after administration of PCPA, PCA, or saline vehicle. There was an excellent correlation between regional 5-HT levels and specific [3H]paroxetine binding in control and PCA-treated rats although this correlation was lost after PCPA treatment. Under these conditions, the 5-HT innervation remains unchanged whereas the concentration of 5-HT and 5-HIAA is greatly reduced. Thus, [3H]paroxetine binding appears to provide a reliable marker of 5-HT innervation density within the mammalian CNS.
Hôpital Louis-H. Lafontaine, Département de Psychiatrie, Montréal, Québec, Canada.
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Grondin
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Carli
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Lima
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D000818:Animals; D001921:Brain / Q000378:metabolism*; D010134:Fenclonine / Q000494:pharmacology*; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D008297:Male; D017374:Paroxetine; D010880:Piperidines / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000378:metabolism*; D012702:Serotonin Antagonists / Q000378:metabolism; D014018:Tissue Distribution; D014316:Tritium; D010133:p-Chloroamphetamine / Q000494:pharmacology*
D010880:Piperidines; D012702:Serotonin Antagonists; D014316:Tritium; D012701:Serotonin; D017374:Paroxetine; D006897:Hydroxyindoleacetic Acid; D010133:p-Chloroamphetamine; D010134:Fenclonine