4-( sup 125 I)iodo-(2,5-dimethoxy)phenylisopropylamine and ( sup 3 H)ketanserin labeling of 5-hydroxytryptamine2 (5HT2) receptors in mammalian cells transfected with a rat 5HT2 cDNA: Evidence for multiple states and not multiple 5HT2 receptor subtypes

Journal Article · Wed Oct 31 23:00:00 EST 1990 · Molecular Pharmacology; (USA)

OSTI ID:6073422

Teitler, M; Leonhardt, S; Weisberg, E L; Hoffman, B J ^[1]

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1. Albany Medical College, NY (USA)

Evidence has accumulated indicating that the radioactive hallucinogens 4-bromo-(3H)(2,5-dimethoxy)phenylisopropylamine ((3H)DOB) and 4-(125I)iodo-(2,5-dimethoxy)phenylisopropylamine ((125I)DOI) label an agonist high affinity state of the 5-hydroxytryptamine2 (5HT2) receptor and (3H)ketanserin labels both agonist high and low affinity states. Recently, an alternative hypothesis has been put forward proposing that the radioactive hallucinogens are labeling a 5HT2 receptor subtype distinct from the receptor labeled by (3H)ketanserin. In order to provide definitive evidence as to which of these hypotheses is correct, the rat 5HT2 receptor gene was transfected into NIH-3T3 cells and COS cells. Neither nontransfected cell type expresses 5HT2 receptors; the transfected cells expressed high affinity binding sites for both (125I) DOI (KD = 0.8 nM and Bmax = 363 fmol/mg in NIH-3T3 cells; KD = 0.2 nM and Bmax = 26 fmol/mg in COS cells) and (3H)ketanserin (KD = 0.4 nM and Bmax = 5034 fmol/mg in NIH-3T3 cells; KD = 1.0 nM and Bmax = 432 fmol/mg in COS cells). The affinities of agonists and antagonists for the (125I)DOI-labeled receptor were significantly higher than for the (3H)ketanserin-labeled receptor. The affinities of agonists and antagonists for these binding sites were essentially identical to their affinities for the sites radiolabeled by these radioligands in mammalian brain homogenates. The (125I)DOI binding was guanyl nucleotide sensitive, indicating a coupling to a GTP-binding protein. These data indicate that the 5HT2 receptor gene product contains both the guanyl nucleotide-sensitive (125I)DOI binding site and the (3H)ketanserin binding site. Therefore, these data indicate that the 5HT2 receptor gene product can produce a high affinity binding site for the phenylisopropylamine hallucinogen agonists as well as for the 5HT2 receptor antagonists.

• OSTI ID: 6073422
• Journal Information: Molecular Pharmacology; (USA), Journal Name: Molecular Pharmacology; (USA) Vol. 38:5; ISSN MOPMA; ISSN 0026-895X
• Country of Publication: United States
• Language: English

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550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AFFINITY
AMINES
ANIMAL CELLS
ANIMALS
AROMATICS
AZAARENES
AZOLES
BETA DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
CENTRAL NERVOUS SYSTEM AGENTS
CONNECTIVE TISSUE CELLS
DAYS LIVING RADIOISOTOPES
DRUGS
ELECTRON CAPTURE RADIOISOTOPES
FIBROBLASTS
GENES
GENETIC ENGINEERING
HALLUCINOGENS
HETEROCYCLIC COMPOUNDS
HYDROGEN COMPOUNDS
INDOLES
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LABELLING
MAMMALS
MEMBRANE PROTEINS
MICE
MONKEYS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PRIMATES
PROTEINS
PSYCHOTROPIC DRUGS
PYRROLES
RADIOISOTOPES
RATS
REACTION KINETICS
RECEPTORS
RODENTS
SOMATIC CELLS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
TRYPTAMINES
VERTEBRATES