Detection and Characterization of the Serotonin 5‐HT1D Receptor in Rat and Human Brain

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Abstract
In the presence of 1 .mu.M (.+-.)-pindolol [to block 5-hydroxytryptamine (5-HT, serotonin) 5-HT1A and 5-HT1B receptors] and 100 nM mesulergine (to block 5-HT1C receptors), 2.0 nM [3H]5-HT binding to rat cortical homogenates is specific, saturable, and reversible. Scatchard analysis of [3H]5-HT binding, in the presence of 1 .mu.M (.+-.)-pindolol and 100 nM mesulergine, produced a KD of 3.2 nM and Bmax of 43 fmol/mg protein. Distribution studies show this site to be present in most rat brain regions. This site is also detectable in human caudate. The pharmacological profile of this site is distinct from the previously identified 5-HT receptor subtypes. Compounds with high affinity for 5-HT1A (8-hydroxydipropylaminotetralin), 5-HT1B (trifluoromethylphenylpiperazine), 5-HT1C (mesulergine, 5-HT2 (4-bromo-2,5-dimethoxyphenylisopropylamine), and 5-HT3 (ICS 205-930) receptors have low affinity for this site. These data suggest the presence of an additional, previously unidentified, 5-HT binding site in rat and human brain tissue. This putative novel 5-HT receptor has a similar pharmacology to the "5-HT1D" site detected in bovine brain by Heuring and Peroutka.

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