Characterization of (/sup 3/H)pirenzepine binding to muscarinic cholinergic receptors solubilized from rat brain
Membranes prepared from rat cerebral cortex were solubilized in buffer containing 1% digitonin. Material present in the supernatant after centrifugation at 147,000 X g was shown to contain binding sites for both (/sup 3/H)quinuclidinyl benzilate ((/sup 3/H)QNB) and (/sup 3/H)pirenzepine ((/sup 3/H)PZ). Recovery of binding sites was approximately 25% of the initial membrane-bound (/sup 3/H)QNB binding sites. The Kd values for (/sup 3/H)QNB and (/sup 3/H)PZ binding to solubilized receptors were 0.3 nM and 0.1 microM, respectively. As has been observed previously in membrane preparations, (/sup 3/H)PZ appeared to label fewer solubilized binding sites than did (/sup 3/H)QNB. Maximum binding values for (/sup 3/H)PZ and (/sup 3/H)QNB binding to solubilized receptors were approximately 400 and 950 fmol/mg of protein, respectively. Competition curves for PZ inhibiting the binding of (/sup 3/H)QNB, however, had Hill slopes of 1, with a Ki value of 0.24 microM. The k1 and k-1 for (/sup 3/H)PZ binding were 3.5 X 10(6) M-1 min-1 and 0.13 min-1, respectively. The muscarinic receptor antagonists atropine, scopolamine and PZ inhibited the binding of (/sup 3/H)QNB and (/sup 3/H)PZ to solubilized receptors with Hill slopes of 1, as did the muscarinic receptor agonist oxotremorine. The muscarinic receptor agonist carbachol competed for (/sup 3/H)QNB and (/sup 3/H)PZ binding with a Hill slope of less than 1 in cerebral cortex, but not in cerebellum. GTP did not alter the interactions of carbachol or oxotremorine with the solubilized receptor. Together, these data suggest that muscarinic receptor sites solubilized from rat brain retain their abilities to interact selectively with muscarinic receptor agonists and antagonists.
- Research Organization:
- Univ. of Pennsylvania, Philadelphia
- OSTI ID:
- 5221138
- Journal Information:
- J. Pharmacol. Exp. Ther.; (United States), Journal Name: J. Pharmacol. Exp. Ther.; (United States) Vol. 1; ISSN JPETA
- Country of Publication:
- United States
- Language:
- English
Similar Records
/sup 3/H)pirenzepine and (-)-(/sup 3/H)quinuclidinyl benzilate binding to rat cerebral cortical and cardiac muscarinic cholinergic sites. I. Characterization and regulation of agonist binding to putative muscarinic subtypes
/sup 3/H)pirenzepine and (-)-(/sup 3/H)quinuclidinyl benzilate binding to rat cerebral cortical and cardiac muscarinic cholinergic sites. II. Characterization and regulation of antagonist binding to putative muscarinic subtypes
Related Subjects
59 BASIC BIOLOGICAL SCIENCES
ACETYLCHOLINE
ADDITIVES
AMINES
AMMONIUM COMPOUNDS
ANIMALS
AUTONOMIC NERVOUS SYSTEM AGENTS
BIOCHEMICAL REACTION KINETICS
BODY
BRAIN
CELL CONSTITUENTS
CELL MEMBRANES
CENTRAL NERVOUS SYSTEM
CHEMICAL BONDS
DETERGENTS
DRUGS
EMULSIFIERS
ESTERS
IN VITRO
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
MAMMALS
MEMBRANES
NERVOUS SYSTEM
NEUROREGULATORS
ORGANIC COMPOUNDS
ORGANS
PARASYMPATHOLYTICS
PARASYMPATHOMIMETICS
QUATERNARY COMPOUNDS
RATS
REACTION KINETICS
RECEPTORS
RODENTS
SOLUBILITY
SURFACTANTS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
VERTEBRATES
WETTING AGENTS