Autoradiographic mapping of 5-HT1B and 5-HT1D receptors in the post mortemhuman brain using [H-3]GR 125743

The distribution of 5-HT1B and 5-HT1D receptors in the human post mortem br ain was examined using whole hemisphere autoradiography and the radioligand [H-3]GR 125743. [H-3]GR 125743 binding was highest in the substantia nigra and the globus pallidus. Lower levels were detected in the striatum, with the highest densities in the ventromedial parts. In the amygdala, the hippo campus, the septal region and the hypothalamus, lower [H-3]GR 125743 bindin g was observed. reflecting low densities of 5-HT1B/1D receptors. In the cer ebral cortex, binding was similar in most regions, although restricted part s of the medial occipital cortex were markedly more densely labeled. Bindin g densities were very low in the cerebellar cortex and in the thalamus. Two methods were used to distinguish between the two receptor subtypes, the fi rst using ketanserin to block 5-HT1D receptors and the second using SB 2242 89 to inhibit 5-HT1B receptor binding. The autoradiograms indicated that in the human brain, the 5-HT1B receptor is much more abundant than the 5-HT1D receptor, which seemed to occur only in low amounts mainly in the ventral pallidum. Although [H-3]GR 125743 is a suitable radioligand to examine the distribution of 5-HT1B receptors in the human brain in vitro, the selectivi ties of ketanserin and SB 224289 are not sufficiently high to give definite evidence for the occurrence of the 5-HT1D receptor in the human brain. (C) 2001 Elsevier Science BY All rights reserved.