Brain trptophan metabolism remained unaltered in restraint stressed rats following fluoxetine administration

Effects of two hours immobilization stress on tryptophan [Tp] metabolism in rats was studied following fluoxetine-HCl [20mg/kg] administration. After 2hr immobilization stress there was no effect on peripheral liver Tp metabolism but there was marked increase in brain Tp metabolism leading to increases in 5-HT [5-Hydroxy tryptamine] synthesis and turn over. Rats subjected to 2hrs immobilization stress immediately after fluoxetine-HCl [20mg/kg] administrations show significant increases in holo and total Tp pyrrolase enzyme activities leading to decreased serum total Tp concentrations. Brain Tp and 5-HT remain unchanged but 5-hydroxy indole acetic acid [5-HIAA] concentration was significantly increased when compared to fluoxetine injected non-immobilized rats. Administration of fluoxetine-HCl [20mg/kg] inhibited holo and total Tp pyrrolase enzyme activities when compared to saline injected rats and ultimately increases liver Tp concentrations. Although serum total Tp remained un- changed but brain Tp and 5-HT concentrations were significantly increased. It is therefore concluded that pre-treatment of rats with fluoxetine-HCl did not alter conditioned stress induced change in brain Tp metabolism. Future studies on chronic administration of the drug will be fruit full to investigate its effects on Tp metabolism in conditioned stress

Rat brain serotonin metabolism following single and repeated administration of sodium salicylate

Single administration of sodium salicylate at dose of 400 mg/kg increased plasma total and free trytophan levels as well as brain levels of tryptophan, 5-hydroxytryptamine [5-HT] and 5-bydroxyindoleacetic acid [5-HIAA]. Administration of sodium salicylate at dose of 100 mg/kg daily for 5 days also increased plasma total, free tryptophan, brain tryptophan, 5-HT and 5-HIAA concentration 24th after the last administration. Administration of sodium salicylate at doses of 400 mg/kg to rats already injected 100mg/kg sodium salicylate for five days potentiated the effects of sodium salicylate on the enhancement of plasma tryptophan, brain tryptophan and 5-HIAA concentrations. These findings together with our previous reports show that repeated administration of analgesia drugs may increase the availability of tryptophan to the brain for the synthesis of 5-HT