SINGLE-PHOTON EMISSION TOMOGRAPHY (SPET) IMAGING OF DOPAMINE D-2 RECEPTORS IN THE COURSE OF DOPAMINE REPLACEMENT THERAPY IN PATIENTS WITH NOCTURNAL MYOCLONUS SYNDROME (NMS)

Single photon emission tomography (SPET) permits the in vivo measureme nts of regional cerebral radioactivity in the human brain following th e administration of compounds labeled with photon-emitting isotopes. A ccording to our SPET findings of a reduced binding of [I-123]labeled - 3-iodo-6-methoxy-([1-ethyl-2-pyrrolidinyl]methyl) benzamide (IBZM) (a highly selective CNS D-2 dopamine receptor ligand) to D-2 dopamine rec eptors in striatal structures in untreated patients with nocturnal myo clonus syndrome (NMS) it seemed to be of interest to investigate wheth er there are changes in D-2 receptor binding under dopamine replacemen t therapy or not. We studied the uptake and distribution of [I-123]IBZ M before and in the course of dopamine replacement therapy in four pat ients with severe insomnia caused by a nocturnal myoclonus syndrome (N MS). We found an increase of the IBZM binding to D-2 receptors in the course of treatment, which was associated with an improvement of sleep quality. Reasons for this are discussed. The [I-123]IBZM SPET techniq ue in conclusion offers an interesting tool for in vivo investigations of functional changes in the dopaminergic neurotransmitter system in longitudinal studies.