[I-123] IBZM SPET ANALYSIS OF DOPAMINE D-2 RECEPTOR OCCUPANCY IN NARCOLEPTIC PATIENTS IN THE COURSE OF TREATMENT

Elevated levels of central D-2 dopamine receptors were found on postmo rtem examination in cases of human narcolepsy, In vivo investigations using positron emission tomography (PET) and single photon emission to mography (SPET) found no changes of D-2 binding in the striatal struct ures. To investigate whether the elevated D-2 receptors in postmortem investigations are due to long-term treatment effects, we applied I-12 3-labeled -3-iodo-6-methoxy-([1-ethyl-2-pyrrolidinyl]methyl) benzamide (IBZM) ([I-123]IBZM, a highly selective CNS D2 dopamine receptor liga nd) and SPET in narcoleptic patients in the course of treatment with s timulants and/or antidepressants. Before treatment we found no changes in D-2 binding in 10 patients (in comparison to 10 normal controls). After treatment (performed in five patients for 3 months) we found cha nges in D-2 binding in four of them, indicating that the results of th e postmortem studies could have been influenced by long-term medicatio ns. Human narcolepsy seems not to be related to a striatal O-2 dopamin ergic disturbance.