Decreased frontal serotonin 5-HT2a receptor binding index in deliberate self-harm patients

Studies of serotonin metabolites in body fluids in attempted suicide patien ts and of post-mortem brain tissue of suicide victims have demonstrated the involvement of the serotonergic neurotransmission system in the pathogenes is of suicidal behaviour. Recently developed neuroimaging techniques offer the unique possibility of investigating in vivo the functional characterist ics of this system. In this study the 5-HT2a receptor population of patient s who had recently attempted suicide was studied by means of the highly spe cific radio-iodinated 5-MT2a receptor antagonist 4-amino-N-[1-[3-(4-fluorop henoxy) propyl] -4-methyl-4-piperidinyl] -5-iodo-2-methoxybenzamide or I-12 3-5-I-R91150. Nine patients who had recently (1-7 days) attempted suicide a nd 12 age-matched healthy controls received an intravenous injection of 185 MBq I-123-5-I-R91150 and were scanned with high-resolution brain single-ph oton emission tomography (SPET), Stereotactic realigned images were analyse d semi-quantitatively using predefined volumes of interest. Serotonin bindi ng capacity was expressed as the ratio of specific to non-specific activity . The cerebellum was used as a measure of non-specific activity. An age-dep endent 5-HT2a binding index was found, in agreement with previous literatur e, Deliberate self-harm patients had a significantly reduced mean frontal b inding index after correction for age (P=0.002) when compared with controls . The reduction was more pronounced among deliberate self-injury patients ( DSI) (P<0.001) than among deliberate self-poisoning patients (DSP). Frontal binding index was significantly lower in DSI patients than in DSP suicide attempters (P<0.001). It is concluded that brain SPET of the 5-MT2a seroton in receptor system in attempted suicide patients who are free of drugs infl uencing the serotonergic system shows in vive evidence of a decreased front al binding index of the 5-HT2a receptor, indicating a decrease in the numbe r and/or in the binding affinity of 5-MT2a receptors.