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Serotonergic systems in brain and blood under stress and tranylcypromine treatment in rats
J Malyszko1, T Urano, Y Takada
1Department of Physiology, Hamamatsu University School of Medicine, Shizuoka, Japan.
Abstract:
The effects of stress on serotonin (5-hydroxytryptamine, 5-HT), 5-hydroxyindole-3-acetic acid (5-HIAA), and/or tryptophan in whole blood and various brain areas of rats pretreated with tranylcypromine were studied. In the whole blood, tranylcypromine given alone caused a rise in levels of 5-HT and a fall in levels of its metabolite (5-HIAA) and the ratio of 5-HIAA:5-HT, whereas in stressed rats pretreated with tranylcypromine only the last two findings were observed. We found that animals given tranylcypromine and subjected to water-immersion restraint stress exhibited the greatest rise in 5-HT levels in midbrain, hippocampus, and hypothalamus, together with the lowest 5-HIAA:5-HT ratio relative to controls, whereas in cortex, cerebellum, medulla, and striatum the highest levels of 5-HT together with the lowest ratio of 5-HIAA:5-HT were observed after the administration of tranylcypromine alone. 5-HT levels were found to be higher in medulla and striatum in rats given tranylcypromine alone relative to stressed rats pretreated with this drug. We concluded that regional differences account for variable effects of tranylcypromine on blood and brain serotonergic systems in vivo.