DOPAMINE D-2-RECEPTORS IN HUMAN NARCOLEPSY - A SPECT STUDY WITH I-123IBZM

Increased dopamine D-2 receptor binding in basal ganglia has been repo rted in human narcolepsy. These studies have been based on post-mortem material of 8 patients, most of them also medicated for narcolepsy. W e studied six narcoleptics without stimulant or anticataplectic medica tion. The patients had an unambiguous history of cataplexy, and they w ere also studied polygraphically. Single photon emission computed tomo graphy (SPECT) imaging was performed. The D-2 receptor density was det ermined by using I-123-iodobenzamide (IBZM). The control subjects were 8 unmedicated Parkinson patients with one-sided (hemiparkinsonian) cl inical symptoms. The D-2 receptor density in them is known to be norma l or somewhat increased compared to healthy normals. The striatum/fron tal D-2 activity ratio was 1.331 +/- 0.084 (with phantom study correct ion 2.101 +/- 0.300) in the narcoleptic patients, and in the parkinson ian controls 1.321 +/- 0.052 (2.067 +/- 0.185) for the asymptomatic si de and 1.335 +/- 0.025 (2.117 +/- 0.090) for the symptomatic side (i.e . contralateral to the side with the clinical extrapyramidal signs). T here was no statistical difference between the groups or between the s ymptomatic and asymptomatic side in the Parkinson patients. Thus, our results differ from the earlier post-mortem studies.