Serotonin turnover rate, [3H]paroxetine binding sites, and 5-HT1A receptors in the hippocampus of rats subchronically treated with clonazepam.
Selective central benzodiazepine agonists, such as clonazepam, are known to modify serotonin and 5-hydroxyindoleacetic content in the brain. In order to further study the effect of this benzodiazepine on serotonin turnover rate, rats received clonazepam, 10 mg/kg for 10 days, and the concentrations of serotonin and 5-hydroxyindoleacetic acid were determined in the hippocampus after inhibition of monoamineoxidase with pargyline. The results indicate a reduction in the turnover rate of the monoamine. In addition, the systemic administration of clonazepam produced a decrease in the Bmax of [3H]DPAT binding to 5-HT1A sites in the hippocampus. By contrast, this effect was not observed if clonazepam was delivered into the dorsal raphe nucleus by osmotic minipumps. The binding of [3H]paroxetine to 5-HT reuptake sites was increased by the treatment with clonazepam. The present observations indicate that clonazepam produces a reduction of serotonin turnover rate in the hippocampus of the rat concomitant with a down-regulation of 5-HT1A binding sites, probably by an effect at the forebrain projections. There is also an up-regulation of the serotonin transporter, which might contribute to a reduction in the synaptic availability of serotonin during clonazepam treatment.
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Laboratorio de Neuroquímica, Instituto Venezolano de Investigaciones Científicas, Caracas, Venezuela.
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D000818:Animals; D001665:Binding Sites; D002065:Buspirone / Q000494:pharmacology; D002998:Clonazepam / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D017374:Paroxetine / Q000378:metabolism*; D011869:Radioligand Assay; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000378:metabolism*; D013997:Time Factors
D012701:Serotonin; D017374:Paroxetine; D002998:Clonazepam; D002065:Buspirone