Indirect estimations of brain neurotransmitters in patients with anorexia nervosa (AN) and low weight have demonstrated a reduction in brain serotonin (5-HT) turnover in general and led to hypotheses about dysfunction in the 5-HT(2a) receptor system. It was our aim to investigate the central 5-HT(2a) receptor binding index using SPECT brain imaging.
Methods: The 5-HT(2a) receptors of low-weight patients with AN were studied by means of the highly specific radioiodinated 5-HT(2a) receptor antagonist 4-amino-N-[1-[3-(4-fluorophenoxy)propyl]-4-methyl-4-piperidinyl]-5-iodo-2-methoxybenzamide or (123)I-5-I-R91150. Fifteen patients with clinical diagnoses of AN and 11 age-matched healthy volunteers received intravenous injections of 185 MBq (123)I-5-I-R91150 and were scanned with high-resolution brain SPECT.
Results: Compared with healthy volunteers, patients with AN had a significantly reduced 5-HT(2a) binding index in the left frontal cortex, the left and right parietal cortex, and the left and right occipital cortex. A significant left-right asymmetry was noted in the frontal cortex (left < right).
Conclusion: These results are in accordance with diminished metabolic and perfusion of frontal and parietal cortices reported in recent neuroimaging studies and imply localized disturbed serotonergic function. The data are discussed in the light of possible confounding factors related to the low-weight AN status. A regional cortical reduction in 5-HT(2a) binding index is not likely to be caused by a general reduction in serotonergic function due to the possible confounding factors. Suggestions for further research are given.