Norepinephrine alterations under stress conditions following the regular practice of meditation

The present study reexamined an investigation that found enhanced plasma norepinephrine (NE) levels during isometric handgrip after 30 days of meditation practice. Since hemodynamic activity did not show corresponding increases, it was suggested that meditation had down regulated the cardiovascular response to sympathetic stimulation. The present study assessed response to venipuncture as well as isometric stress. At posttest, meditators showed a trend towards higher plasma NE levels than controls during isometric handgrip. However, in contrast to previous speculation, this did not appear to represent cardiovascular down-regulation. At the same time, meditators produced the greater NE levels during venipuncture, accompanied by marginally lower heart rate. The results support the association between regular meditation and noradrenergic hyperactivation, but suggest the need for further investigation of underlying mechanisms.