The distribution of serotonin receptors in the human brain: high density of [3H]LSD binding sites in the raphe nuclei of the brainstem.

Serotonin receptors were localized autoradiographically in the human brainstem after in vitro labeling using [3H]lysergic acid diethylamide (LSD). Very high concentration of [3H]LSD binding sites, apparently belonging to the 5-HT1 class were localized in the raphe nuclei. Other areas of the brainstem presented only moderate or low receptor densities. Labeled areas were the nucleus interpeduncularis, periaqueductal gray matter, locus coeruleus and nucleus tractus solitarius. The choroid plexus was also labeled by [3H]LSD. The use of [3H]LSD binding as a marker for serotonin cells in the brainstem is suggested.