Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

The Effects of L-Dihydroxyphenylalanine on Alertness and Mood in α-Methyl-Para-Tyrosine-Treated Healthy Humans

Further Evidence for the Role of Catecholamines in Arousal and Anxiety


Treatment with α-methyl-para-tyrosine (AMPT), a catecholamine synthesis inhibitor, has been shown to produce pronounced increases in sleepiness and mild increases in negative mood and anxiety when administered to healthy male adults. The present study was conducted to ascertain whether these effects of AMPT are secondary to decreases in brain catecholamines or whether they represent nonspecific drug effects. Forty-one healthy males were randomized to one of four treatment groups. (1) Treatment with AMPT alone (AMPT/placebo); (2) treatment with AMPT plus L-dopa/carbidopa (AMPT plus L-dopa/carbidopa); (3) treatment with L-dopa/carbidopa alone (placebo plus L-dopa/carbidopa); or (4) treatment with placebo alone (placebo plus placebo). Repeated measures of alertness, mood, and anxiety were obtained over a three-day period of drug treatment and following drug discontinuation. As before, AMPT treatment led to increased sleepiness. In addition, AMPT treatment led to decreased calmness, increased tension and anger, and a trend for increased depression. Replacement of catecholamine stores with L-dopa reversed the effects of AMPT and was associated with a more rapid recovery from AMPT's effects. These findings indicate that AMPT's effects on alertness and anxiety are catecholamine-specific. Further, they provide additional evidence that catecholamines are involved in the regulation of normal states of arousal, and they are consistent with the view that brain catecholaminergic dysregulation is involved in pathological anxiety states.

Author information



Corresponding author

Correspondence to Una D McCann MD.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

McCann, U., Thorne, D., Hall, M. et al. The Effects of L-Dihydroxyphenylalanine on Alertness and Mood in α-Methyl-Para-Tyrosine-Treated Healthy Humans. Neuropsychopharmacol 13, 41–52 (1995).

Download citation


  • Catecholamines
  • Arousal
  • Mood
  • Anxiety
  • AMPT
  • L-dopa
  • Carbidopa

Further reading


Quick links