Molecular Pharmacology, Vol 17, 285-289, Copyright © 1980 by the American Society for Pharmacology and Experimental Therapeutics

Characterization of -Aminobutyric Acid Receptor Binding in Cultured Brain Cells

¹ Division of Molecular Pharmacology, Department of Pharmacology, The University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, Texas 78284
² Laboratory of Neurophysiology, NINCDS-NIH, Bethesda, Maryland 20205

The binding of the inhibitory neurotransmitter -[³H]aminobutyric acid to its receptor sites was investigated in extensively washed membranes of primary brain cultured cells. Extensive washing of the brain cultured cells was necessary to eliminate the endogenous inhibitors of -aminobutyric acid receptor binding. The binding of -[³H]aminobutyric acid to cultured brain cells was specific, rapid, and saturable. Scatchard analysis of the binding data revealed the presence of two classes of sites. The high-affinity site had a K_D1 of 9 nM and a B_max1 of 380 fmol/mg protein, and the low-affinity site had a K_D2 of 250 nM and a B_max2 of 2400 fmol/mg protein. The specific binding was displaced by muscimol (IC₅₀ = 0.005 µM), -aminobutyric acid (IC₅₀ = 0.025 µM), and (+)-bicuculline (IC₅₀ = 4 µM). Specific binding was not inhibited by nipecotic acid, picrotoxin, or pentobarbital. On the basis of saturation, classes of sites, affinity constants, and ligand specificity, it appears that cultured brain cells have -aminobutyric acid receptors which appear identical to those found in mammalian brain.

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ACKNOWLEDGMENTS We thank Dr. M. Javors for reading the manuscript and Ms. M. Wilson for excellent secretarial help.