5-hydroxytryptamine (serotonin) receptor 1D, also known as HTR1D, is a 5-HT receptor, but also denotes the human gene encoding it. 5-HT1D acts on the central nervous system, and affects locomotion and anxiety. It also induces vasoconstriction in the brain.
Tissue distribution and function
5HT1D receptors are found at low levels in the basal ganglia (globus pallidus, substantia nigra, caudate putamen), the hippocampus, and in the cortex.
5HT1D receptor is a G protein linked receptor that activates an intracellular messenger cascade to produce an inhibitory response by decreasing cellular levels of cAMP. The 5HT1D is a 7-TM receptor. A large intercellular loop between TM-5 and TM-6 is believed to be associated with coupling to a second messenger. Agonists might bind in a manner that utilizes an aspartate residue in TM-3 and residues in the TM-4, TM-5 and TM-6. A human clone containing an intronless open reading frame was found to encode 377 amino acids of the 5HT1D receptor. The gene has been localized on chromosome 1, region 1p34.3-36.3 
Molecular modelling has provided a picture of the agonistic binding site of 5HT1D. The amino acid residues within the receptor binding site region have been identified. This is a valuable guide to design potential 5HT1D receptor agonists.
When sumatriptan binds there is major conformational change in both ligand and receptor in the binding pocket.
- Sumatriptan (vasoconstrictor in migraine)
- 5-Carboxamidotryptamine (5-CT)
- PNU-109,291 ((S)-3,4-Dihydro-1-[2-[4-(4-methoxyphenyl)-1-piperazinyl]ethyl]-N-methyl-1H-2-benzopyran-6-carboxamide)
- PNU-142,633 ((1S)-1-[2-[4-[4-(Aminocarbonyl)phenyl]-1-piperazinyl]ethyl]-3,4-dihydro-N-methyl-1H-2-benzopyran-6-carboxamide)
- GR-46611 (3-[3-(2-Dimethylaminoethyl)-1H-indol-5-yl]-N-(4-methoxybenzyl)acrylamide)
- L-694,247 (2-[5-[3-(4-Methylsulfonylamino)benzyl-1,2,4-oxadiazol-5-yl]-1H-indol-3-yl]ethanamine)