Selective antagonism of rat inhibitory glycine receptor subunits.
Retinal ganglion cells exhibit fast and slow inhibitory synaptic glycine currents that can be selectively inhibited by strychnine and 5,7-dichlorokynurenic acid (DCKA), respectively. In this study we examined whether strychnine and DCKA selectivity correlated with the subunit composition of the glycine receptor. Homomeric alpha1, alpha2 or alpha2* glycine subunits were in vitro expressed in human embryonic kidney cells (HEK 293). In cells expressing the alpha1 subunit, responses to 200 microm glycine were blocked by 1 microm strychnine but not by 500 microm DCKA. In cells expressing the alpha2 subunit, both 1 microm strychnine and 500 microm DCKA were effective antagonists of 200 microm glycine. In cells expressing alpha2* subunits, which are much less glycine-sensitive, 10 mm glycine was inhibited by 500 microm DCKA but not by 1 microm strychnine. A single amino acid mutation in the alpha1 subunit (R196G), converted this subunit from DCKA-insensitive to DCKA-sensitive. In conclusion, the comparative effectiveness of strychnine and DCKA can be used to distinguish between the alpha1, alpha2 and alpha2* receptor responses. Furthermore, a single amino acid near the glycine receptor's putative agonist binding site may account for differences in DCKA sensitivity amongst the alpha subunits.
Han
Yi
Y
University at Buffalo School of Medicine, Department of Physiology & Biophysics, 124 Sherman Hall, 3435 Main Street, Buffalo, NY 14214, USA.
Li
Ping
P
Slaughter
Malcolm M
MM
D000818:Animals; D001120:Arginine; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D018691:Excitatory Amino Acid Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D005998:Glycine / Q000008:administration & dosage / Q000037:antagonists & inhibitors / Q000494:pharmacology; D018684:Glycine Agents / Q000008:administration & dosage / Q000494:pharmacology*; D006801:Humans; D007736:Kynurenic Acid / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology*; D009154:Mutation; D009994:Osmolar Concentration; D051381:Rats; D018009:Receptors, Glycine / Q000037:antagonists & inhibitors* / Q000235:genetics; D013331:Strychnine / Q000008:administration & dosage / Q000494:pharmacology*
D018691:Excitatory Amino Acid Antagonists; C439504:GLRA2 protein, human; C501174:Glra2 protein, rat; D018684:Glycine Agents; D018009:Receptors, Glycine; D001120:Arginine; D007736:Kynurenic Acid; D013331:Strychnine; C066192:5,7-dichlorokynurenic acid; D005998:Glycine