State Anxiety, Physical Activity, and Urinary 3-Methoxy-4-Hydroxyphenethylene Glycol Excretion

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Abstract
Measurement of urinary 3-methoxy-4-hydroxyphenethylene glycol (MHPG) levels has been suggested as possibly being important in elucidating the role of central noradrenergic function in affective illnesses. The influence on urinary MHPG excretion of the state variables of physical activity and stress has not been clearly defined in previous studies. During a baseline medication-free period, 24 hospitalized depressed female patients underwent a five-day protocol including an eight-hour period of either enhanced or restricted activity. Throughout the protocol, independent measurements of telemetered mobility and stale anxiety were obtained. There were no significant effects of physical activity on urinary MHPG levels. Furthermore, baseline urinary MHPG levels and baseline state anxiety did not covary significantly. However, within-individual analyses yielded a highly significant relationship between changes in urinary MHPG levels and changes in state anxiety. The data suggested that those patients with lower baseline MHPG levels were those more prone to experience increased anxiety under environmentally "activating" circumstances.