DIFFERENTIAL-EFFECTS OF NORADRENERGIC DRUGS ON ANXIETY AND AROUSAL INHEALTHY-VOLUNTEERS WITH HIGH AND LOW ANXIETY

1. The appearance of frontal midline theta activity (Fm theta), the di stinct EEG theta rhythm in the frontal midline area during performance of a mental task, indicates relief from anxiety in humans. 2. The aut hors investigated the effects of clonidine and yohimbine on anxiety an d arousal in 24 male university students with (Fm theta group, n=12) a nd without (non-Fm theta group, n=12) Fm theta. Subjects received plac ebo, 0.15 mg clonidine and 15 mg yohimbine in a double-blind crossover design. 3. Blood samples were obtained, state-trait anxiety inventory (STAI) scores were determined, and EEGs were recorded before and duri ng the performance of an arithmetic addition task. The test was repeat ed twice: before and 1 hr after drug administration. 4. Clonidine redu ced the 3-methoxy-4-hydroxyphenylglycol (MHPG) concentration in both g roups; yohimbine caused an increase in both groups. In the Fm theta gr oup, clonidine reduced the appearance time of Fm theta and the number of task performance but did not alter the state anxiety scores; yohimb ine had no effects on Fm theta or the state anxiety but increased the task performance. In the non-Fm theta group, clonidine increased the F m theta amount and reduced the state anxiety score but did not affect task performance, while yohimbine reduced Fm theta but increased the s tate anxiety, the task performance and the number of errors. 5. These results suggest that changes in noradrenaline (NA) activity affect bot h anxiety and arousal levels in high-anxiety humans, but predominantly affect only the arousal level in low-anxiety humans.