Desensitization of. gamma. -aminobutyric acid receptor from rat brain: two distinguishable receptors on the same membrane

Journal Article · Tue Dec 01 04:00:00 EST 1987 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00398a004· OSTI ID:5438040

Cash, D J; Subbarao, K

Transmembrane chloride flux mediated by ..gamma..-aminobutyric acid (GABA) receptor can be measured with a mammalian brain homogenate preparation containing sealed membrane vesicles. The preparation can be mixed rapidly with solutions of defined composition. Influx of /sup 36/Cl/sup -/ tracer initiated by mixing with GABA was rapidly terminated by mixing with bicuculline methiodide. The decrease in the isotope influx measurement due to prior incubation of the vesicle preparation with GABA, which increased with preincubation time and GABA concentration, was attributed to desensitization of the GABA receptor. By varying the time of preincubation with GABA between 10 ms and 50 s with quench-flow technique, the desensitization rates could be measured over their whole time course independently of the chloride ion flux rate. Most of the receptor activity decreased in a fast phase of desensitization complete in 200 ms at saturation with GABA. Remaining activity was desensitized in a few seconds. These two phases of desensitization were each kinetically first order and were shown to correspond with two distinguishable GABA receptors on the same membrane. The receptor activities could be estimated, and the faster desensitizing receptor was the predominant one, giving on average ca. 80% of the total activity. The half-response concentrations were similar, 150 and 114 ..mu..M for the major and minor receptors, respectively. The dependence on GABA concentration indicated that desensitization is mediated by two GABA binding sites. The fast desensitization rate was approximately 20-fold faster than previously reported rates while the slower desensitization rate was slightly faster than previously reported rates.

• Research Organization: Univ. of Missouri, St. Louis
• OSTI ID: 5438040
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 26:24; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALKALINE EARTH METAL COMPOUNDS
AMINO ACIDS
AMINOBUTYRIC ACID
ANIMALS
AUTONOMIC NERVOUS SYSTEM AGENTS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BODY
BRAIN
CALCIUM CHLORIDES
CALCIUM COMPOUNDS
CALCIUM HALIDES
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CELL MEMBRANES
CENTRAL NERVOUS SYSTEM
CHLORIDES
CHLORINE 36
CHLORINE COMPOUNDS
CHLORINE ISOTOPES
DRUGS
ELECTRON CAPTURE RADIOISOTOPES
HALIDES
HALOGEN COMPOUNDS
ISOTOPES
KINETICS
LIGHT NUCLEI
MAGNESIUM CHLORIDES
MAGNESIUM COMPOUNDS
MAMMALS
MEMBRANE PROTEINS
MEMBRANE TRANSPORT
MEMBRANES
NERVOUS SYSTEM
NEUROREGULATORS
NUCLEI
ODD-ODD NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANS
PROTEINS
RADIOISOTOPES
RATS
REACTION KINETICS
RECEPTORS
RODENTS
SENSITIVITY
VERTEBRATES
YEARS LIVING RADIOISOTOPES