Serotonin, noradrenaline, dopamine metabolites in transcendental meditation-technique.

The highly significant increase of 5-HIAA (5-hydroxyindole-3-acetic acid) in Transcendental Meditation technique suggests systemic serotonin as "rest and fulfillment hormone" of deactivation-relaxation. Furthermore 5-HT (5-hydroxytryptamine, serotonin) is considered to be the EC-cell (enterochromaffine-cell) hormone requested by Fujita and Kobayashi and its role for EEG synchronisation via area postrema chemoreceptor as anti arousal agent is being discussed. The significant decrease of the catecholamine metabolite VMA (vanillic-mandelic acid) in meditators, that is associated with a reciprocal increase of 5-HIAA supports as a feedback necessity the "rest and fulfillment response" versus "fight and flight". As the adreno medullary tissue serves for hormonal reinforcement of orthosympathetic activity, the Enterochromaffine Cell System (having taken the form of distinct organs in some species as octopus and discoglossus) is suggested to serve via serotonin for humoral reinforcement of parasympathetic activity in deep relaxation.