Open Access

ARTICLE

Age related interaction of dopamine and serotonin synthesis in striatal synaptosomes

by MANOOCHEHR MESSRIPOUR, AZADEH MESRIPOUR

1 Department of Medical Biochemistry, Khorasgan Branch, Islamic Azad University, Isfahan, Iran
2 Medical Plant Research Center, Shahre Kord University of Medical Sciences, Iran

* Address correspondence to: Manoochehr Messripour. Department of Medical Biochemistry, Khorasgan Branch, Islamic Azad University, Isfahan, IRAN

BIOCELL 2013, 37(2), 17-21. https://doi.org/10.32604/biocell.2013.37.017

Abstract

Tyrosine hydroxylase and tryptophan hydroxylase are key rate limiting enzymes in the biosynthesis of dopamine and serotonin, respectively. Since both enzymes are active in striatum, and affected by age, this study was undertaken to investigate interaction between dopamine and serotonin synthesis in brain striatal synaptosomes of aging rat. Male Wistar rats (3 and 30 month old) were killed by decapitation and brain striatal synaptosomes were prepared by discontinuous Ficoll/sucrose gradient technique. Synaptosomes were incubated in the presence of added pargiline (monoamineoxidase inhibitor), dopamine or serotonin synthesized during 25 min was measured by HPLC, employing electrochemical detection. Dopamine synthesis in synaptosomes prepared from young animals was markedly inhibited by addition of 5 μM serotonin concentrations (30%) and increasing serotonin concentrations up to 50 μM caused only a smaller additional inhibition. Dopamine synthesis in synaptosomes obtained from old rats was signifi cantly lower than that of youg animals and addition of serotonin concentrations up to 50 μM had little effect on these preparations. In case of serotonin synthesis, exogenously added 5 μM dopamine inhibited serotonin synthesis in the synaptosomes of both ages by about 40%, whereas with higher concentration of dopamine (10-50 μM) the rate of inhibition was highly pronounced in old rats as compared to that of young animals. It is concluded that dopamine and serotonin interaction may be signifi cant, and that these should be considered in long-term treatments of Parkinson’s disease with L-DOPA.

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