Determination of the equilibrium dissociation constants and number of glycine binding sites in several areas of the rat central nervous system, using a sodium-independent system.
Parameters affecting the binding of [3H]glycine to membrane fractions isolated from the cerebral cortex, midbrain, cerebellum, medulla oblongata, and spinal cord of the rat were investigated in a Na+-free medium. A [3H]glycine binding assay was established in which the binding was specific, saturable, pH-sensitive, and reversible. Conditions were chosen in an effort to minimize binding to glycine uptake sites. From data on specific [3H]glycine binding Scatchard plots were prepared and the KD and Bmax values were calculated. Two glycine binding sites (high and low affinity) were identified only in the medulla (KD: 44, 211 nM; Bmax: 361, 1076 fmol/mg protein) and spinal cord (KD: 19, 104 nM; Bmax: 105, 486 fmol/mg protein). The ranges of the KD and Bmax values for the other three areas studied were 59 to 144 nM and 882 to 3401 fmol/mg protein, respectively. When the glycine content of each area, expressed as fmol/neuron, was plotted against the respective KD (high affinity), a negative correlation was found (r = --0.90; p less than 0.05). A similar negative correlation was found between the glycine content and Bmax (r = --0.88; p less than 0.05). Hill plots indicated a slope of essentially 1.0 for all areas. GABA, taurine, strychnine, diazepam, bicuculline, and imipramine had little or no effect on [3H]glycine binding.
D000596:Amino Acids / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002531:Cerebellum / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism; D005998:Glycine / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008526:Medulla Oblongata / Q000378:metabolism; D008636:Mesencephalon / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000378:metabolism*; D018009:Receptors, Glycine; D012964:Sodium / Q000494:pharmacology; D013116:Spinal Cord / Q000378:metabolism*; D014018:Tissue Distribution
D000596:Amino Acids; D011956:Receptors, Cell Surface; D018009:Receptors, Glycine; D012964:Sodium; D005998:Glycine