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Abstract
Plasma norepinephrine (NE), free 3-methoxy-4-hydroxyphenethylene glycol (MHPG), and
binding of tritiated yohimbine to platelet membranes were measured in 14 patients
with generalized anxiety disorder (GAD), who were matched for age and sex with 14
patients with unipolar major depressive disorder (MDD) and 14 normal subjects. Plasma
NE and MHPG levels were increased and the number of alpha2-adrenoreceptors (Bmax)
was decreased in GAD patients compared with MDD and normal subjects. No differences
were found between MDD patients and normal subjects for plasma NE, MHPG, and alpha2-adrenoreceptor
binding. Plasma NE and MHPG were significantly correlated in MDD patients and tended
toward a significant positive correlation in GAD patients. Plasma MHPG and affinity
of binding platelet alpha2-adrenoreceptors (Kd) were significantly correlated in normal
subjects. Thus, noradrenergic activity seems to be increased in patients with GAD,
but not in patients with MDD. In GAD patients, higher levels of catecholamines may
lead to a down-regulation of presynaptic alpha2-adrenoreceptors.