Labeling by ( sup 3 H)1,3-di(2-tolyl)guanidine of two high affinity binding sites in guinea pig brain: Evidence for allosteric regulation by calcium channel antagonists and pseudoallosteric modulation by sigma ligands

Journal Article · Fri Feb 01 00:00:00 EST 1991 · Molecular Pharmacology; (USA)

OSTI ID:6057382

Rothman, R B; Reid, A; Mahboubi, A; Kim, C H; De Costa, B R; Jacobson, A E; Rice, K C ^[1]

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1. National Institute of Mental Health, Bethesda, MD (USA)

Equilibrium binding studies with the sigma receptor ligand ({sup 3}H)1,3-di(2-tolyl)guanidine (({sup 3}H)DTG) demonstrated two high affinity binding sites in membranes prepared from guinea pig brain. The apparent Kd values of DTG for sites 1 and 2 were 11.9 and 37.6 nM, respectively. The corresponding Bmax values were 1045 and 1423 fmol/mg of protein. Site 1 had high affinity for (+)-pentazocine, haloperidol, (R)-(+)-PPP, carbepentane, and other sigma ligands, suggesting a similarity with the dextromethorphan/sigma 1 binding site described by Musacchio et al. (Life Sci. 45:1721-1732 (1989)). Site 2 had high affinity for DTG and haloperidol (Ki = 36.1 nM) and low affinity for most other sigma ligands. Kinetic experiments demonstrated that ({sup 3}H)DTG dissociated in a biphasic manner from both site 1 and site 2. DTG and haloperidol increased the dissociation rate of ({sup 3}H)DTG from site 1 and site 2, demonstrating the presence of pseudoallosteric interactions. Inorganic calcium channel blockers such as Cd2+ selectively increased the dissociation rate of ({sup 3}H)DTG from site 2, suggesting an association of this binding site with calcium channels.

• OSTI ID: 6057382
• Journal Information: Molecular Pharmacology; (USA), Vol. 39:2; ISSN 0026-895X
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
ENDORPHINS
RECEPTORS
GUANIDINES
BIOCHEMICAL REACTION KINETICS
LABELLING
AFFINITY
BRAIN
CELL MEMBRANES
ENZYME INHIBITORS
GUINEA PIGS
LIGANDS
PORINS
STRUCTURE-ACTIVITY RELATIONSHIPS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
ANIMALS
AUTONOMIC NERVOUS SYSTEM AGENTS
BODY
CARBONIC ACID DERIVATIVES
CELL CONSTITUENTS
CENTRAL NERVOUS SYSTEM
DRUGS
HYDROGEN COMPOUNDS
ISOTOPE APPLICATIONS
KINETICS
MAMMALS
MEMBRANE PROTEINS
MEMBRANES
NERVOUS SYSTEM
NEUROREGULATORS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
PROTEINS
REACTION KINETICS
RODENTS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques