Pharmacological and ionic characterizations of the muscarinic receptors modulating (/sup 3/H)acetylcholine release from rat cortical synaptosomes
The muscarinic receptors that modulate acetylcholine release from rat cortical synaptosomes were characterized with respect to sensitivity to drugs that act selectively at M1 or M2 receptor subtypes, as well as to changes in ionic strength and membrane potential. The modulatory receptors appear to be of the M2 type, since they are activated by carbachol, acetylcholine, methacholine, oxotremorine, and bethanechol, but not by pilocarpine, and are blocked by atropine, scopolamine, and gallamine (at high concentrations), but not by pirenzepine or dicyclomine. The ED50S for carbachol, acetylcholine, and oxotremorine are less than 10 microM, suggesting that the high affinity state of the receptor is functional. High ionic strength induced by raising the NaCl concentration has no effect on agonist (oxotremorine) potency, but increases the efficacy of this compound, which disagrees with receptor-binding studies. On the other hand, depolarization with either KCl or with veratridine (20 microM) reduces agonist potencies by approximately an order of magnitude, suggesting a potential mechanism for receptor regulation.
- OSTI ID:
- 6432563
- Journal Information:
- J. Neurosci.; (United States), Vol. 5
- Country of Publication:
- United States
- Language:
- English
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CHOLINE
RECEPTORS
BIOCHEMICAL REACTION KINETICS
ACETYLCHOLINE
AFFINITY
CEREBRAL CORTEX
DOSE-RESPONSE RELATIONSHIPS
RATS
TRITIUM COMPOUNDS
ALCOHOLS
AMINES
AMMONIUM COMPOUNDS
ANIMALS
AUTONOMIC NERVOUS SYSTEM AGENTS
BODY
BRAIN
CENTRAL NERVOUS SYSTEM
CEREBRUM
DRUGS
ESTERS
HYDROXY COMPOUNDS
KINETICS
LABELLED COMPOUNDS
LIPOTROPIC FACTORS
MAMMALS
NERVOUS SYSTEM
NEUROREGULATORS
ORGANIC COMPOUNDS
ORGANS
PARASYMPATHOMIMETICS
QUATERNARY COMPOUNDS
REACTION KINETICS
RODENTS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques