D, L-(tetrazol-5-yl)glycine stimulation of NMDA receptors in neonatal dissociated neurons: inhibition by ethanol.
Ethanol inhibition of NMDA receptor stimulation by the high-affinity selective agonist D, L-(tetrazol-5-yl)glycine (T5G) was studied using acutely dissociated neonatal whole-brain neurons loaded with the fluorescent indicator fura-2. T5G induced a concentration-dependent increase in intracellular calcium with a maximal increase above basal of 70nM at 16 microM T5G (EC50 of 0.66 +/- 0.18 microM). T5G agonist specificity was verified using the NMDA antagonists MK-801 (40 nM), APV (100 microM), and Mg2+ (1 mM). The T5G stimulation of calcium entry was both blocked and reversed by these antagonists. Ethanol significantly inhibited the T5G-mediated increase in intracellular calcium only at concentrations > or = 100 mM. In addition, the effect of increasing concentrations of ethanol in the presence of the glycine-site antagonist 5, 7-dichlorokynurenic acid (DCKA, 0.37 microM) on T5G-stimulated calcium entry was examined. A significant inhibition of the T5G-stimulated response in the presence of DCKA was observed at ethanol concentrations as low as 20 mM. These results support previous findings that T5G is a potent agonist of the NMDA receptor and indicate that stimulation of calcium entry by this agonist is less sensitive to ethanol inhibition than stimulation by NMDA.
Jones
T W
TW
Division of Pharmacology and Toxicology, College of Pharmacy, University of Texas at Austin 78712-1074, USA.
Spuhler-Phillips
K
K
Wilson
W
W
Leslie
S W
SW
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology; D002478:Cells, Cultured; D002492:Central Nervous System Depressants / Q000494:pharmacology*; D016291:Dizocilpine Maleate / Q000494:pharmacology; D000431:Ethanol / Q000494:pharmacology*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D016257:Fura-2; D005998:Glycine / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000494:pharmacology; D007736:Kynurenic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000819:agonists*; D013777:Tetrazoles / Q000037:antagonists & inhibitors / Q000494:pharmacology*
D002492:Central Nervous System Depressants; D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; D013777:Tetrazoles; C073649:(tetrazol-5-yl)glycine; D000431:Ethanol; D016291:Dizocilpine Maleate; D015763:2-Amino-5-phosphonovalerate; D007736:Kynurenic Acid; C066192:5,7-dichlorokynurenic acid; D005998:Glycine; D016257:Fura-2