Dopaminergic Instability in Children with Orthostatic Dysregulation

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Abstract
Effects of postural change on plasma catecholamine levels were examined in 53 children with orthostatic dysregulation (OD). Special interest was focused on plasma dopamine and dopamine-beta-hydroxylase (DBH) activity, since one patient showed a prominent rise in plasma dopamine from 822 pmol/L to 126 nmol/L in postural change. She had a wide fluctuation of plasma dopamine from 209 pmol/L to 305 nmol/L during 12 hours of observation period, but plasma norepinephrine and epinephrine remained within the normal range as well as urinary excretion of catecholamines. Of 52 children with OD, 11 had a marked increase in plasma dopamine, whereas 11 showed a reduction of it by postural change. Plasma DBH activity was significantly decreased in the former (81 +/- 14 nmol/h/ml), while it was elevated in the latter (320 +/- 48 nmol/h/ml, P less than 0.001 vs the former), although DBH activity in individuals was not affected by postural change. These results indicate the involvement of dopaminergic instability as a cause of OD in childhood.