Functional and radioligand binding characterization of rat 5-HT6 receptors stably expressed in HEK293 cells

Neuropharmacology. Apr-May 1997;36(4-5):713-20. doi: 10.1016/s0028-3908(97)00019-1.

Abstract

We have stably expressed the rat 5-HT6 receptor in HEK293 cells at a density of > 2 pmol/mg protein, as determined in equilibrium binding studies with [3H]-LSD and [3H]-5-HT and compared the affinity of a range of compounds in competition binding experiments with either [3H]-LSD or [3H]-5-HT as radioligand. A variety of tryptamine derivatives were tested and showed a significantly higher affinity when the 5-HT6 receptor was labelled with [3H]-5-HT, whereas ergoline compounds and several antagonists had higher affinities when [3H]-LSD was used as radioligand. Subsequently we examined the ability of LSD, 5-HT and a number of tryptamine derivatives to stimulate cAMP accumulation in order to determine their agonist potency and efficacy. We observed the following rank order of potency: LSD > omega-N-methyl-5-HT approximately bufotenine approximately 5- methoxytryptamine > 5-HT > 2-methyl-5-HT approximately 5-benzyloxytryptamine approximately tryptamine > 5-carboxamidotryptamine > > 5-HTQ. LSD, lisuride, 2-methyl-5-HT, tryptamine and 5-benzyloxytryptamine behaved as partial agonists relative to 5-HT. The rank order of potency of the tryptamine compounds correlated well with their affinities determined in binding assays. In addition, we have tested a number of antagonists in this system (rank order of potency: methiothepin, clozapine, mianserin and ritanserin). This characterization of the pharmacological properties of recombinant 5-HT6 receptor will facilitate the identification of 5-HT6 receptor-mediated responses in physiological systems.

MeSH terms

  • Adenylyl Cyclases / biosynthesis
  • Animals
  • Cell Line
  • DNA, Complementary / biosynthesis
  • Kinetics
  • Lysergic Acid Diethylamide / metabolism
  • Lysergic Acid Diethylamide / pharmacology
  • Membranes / metabolism
  • Molecular Sequence Data
  • RNA, Messenger / biosynthesis
  • Radioligand Assay
  • Rats
  • Receptors, Serotonin / drug effects*
  • Receptors, Serotonin / genetics
  • Receptors, Serotonin / metabolism
  • Serotonin Antagonists / metabolism
  • Serotonin Antagonists / pharmacology
  • Serotonin Receptor Agonists / metabolism
  • Serotonin Receptor Agonists / pharmacology
  • Transfection
  • Tryptamines / metabolism
  • Tryptamines / pharmacology

Substances

  • DNA, Complementary
  • RNA, Messenger
  • Receptors, Serotonin
  • Serotonin Antagonists
  • Serotonin Receptor Agonists
  • Tryptamines
  • Lysergic Acid Diethylamide
  • Adenylyl Cyclases

Associated data

  • GENBANK/L03203
  • GENBANK/L19656
  • GENBANK/L41146