ABSTRACT
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