Quantitative autoradiography of 5-HT sub(1D) and 5-HT sub(1E) binding sites labelled by [ super(3)H]5-HT, in frontal cortex and the hippocampal region of the human brain

In human cortex and hippocampus area, [ super(3)H]5-HT (5 nM) labels 5-HT sub(1A), 5-HT sub(1D) and 5-HT sub(1E) sites. After masking 5-HT sub(1A) receptors by 8-OH-DPAT, the binding displaced by 5-CT presumably represented 5-HT sub(1D) sites and the remaining binding 5-HT sub(1E) sites. In frontal cortex, 5-HT sub(1A) receptors represented the main binding in layers II and VI and a lower fraction in other layers. 5-HT sub(1D) and 5-HT sub(1E) sites, were more homogeneously distributed in layers II to VI (21-34% of specific [ super(3)H]5-HT binding). 5-HT sub(1E) sites were of similar affinities in the cortical layers II to VI. In CA1 field of hippocampus, (pyramidal layer, stratum radiatum, molecular layer), CA2 and dentate gyrus, 5-HT sub(1A) receptors represented the major fraction, 5-HT sub(1D) sites a significant fraction and 5-HT sub(1E) a minor fraction of the specific [ super(3)H]5-HT binding. In CA3-CA4 fields, 5-HT sub(1A) receptors were less densely present, 5-HT sub(1D) sites were predominant and 5-HT sub(1E) sites represented a significant fraction (27%). The highest densities of 5-HT sub(1E) sites have been measured in subiculum, where 5-HT sub(1A), 5-HT sub(1D) and 5-HT sub(1E) binding sites were equally represented and in entorhinal cortex where 5-HT sub(1E) sites represented the major binding in layer III.