Neurochemical and behavioural effects of long term intake of tea.

Tea consumption in many cases is the main source of caffeine intake in humans. In the present study neurochemical and behavioural effects of long-term tea intake are monitored in rats. Long-term tea administration did not alter plasma tryptophan (TRP) but significantly attenuated brain TRP and 5-hydroxytryptamine (5-HT, serotonin) levels. Brain 5-hydroxyindole acetic acid (5-HIAA) was comparable in both tea-treated and control rats. An increase in home cage activity was observed after one week in rats taking tea as sole source of liquid, whereas no change on the activity was observed in an open field. Caffeinism has been associated with depression. The decreases of brain monoamine metabolism observed in present study are discussed as lowering of mood observed in tea or coffee consumers.