MECHANISM OF INHIBITION OF N-METHYL-D-ASPARTATE-STIMULATED INCREASES IN FREE INTRACELLULAR CA2+ CONCENTRATION BY ETHANOL

被引:125
作者
DILDYMAYFIELD, JE [1 ]
LESLIE, SW [1 ]
机构
[1] UNIV TEXAS, INST NEUROSCI, AUSTIN, TX 78712 USA
关键词
DISSOCIATED BRAIN CELLS; FURA-2; FREE INTRACELLULAR CA2+ CONCENTRATION; N-METHYL-D-ASPARTATE; ETHANOL; GLYCINE; MK-801;
D O I
10.1111/j.1471-4159.1991.tb02048.x
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Dissociated brain cells were isolated from newborn rat pups and loaded with fura-2. These cells were sensitive to low N-methyl-D-aspartate (NMDA) concentrations with EC50 values for NMDA-induced intracellular Ca2+ concentration ([Ca2+])i) increases of approximately 7-16-mu-M measured in the absence of Mg2+. NMDA-stimulated [Ca2+]i increases could be observed in buffer with Mg2+ when the cells were predepolarized with 15 mM KCl prior to NMDA addition. Under these predepolarized conditions, 100 mM ethanol inhibited 25-mu-M NMDA responses by approximately 50%, which was similar to the ethanol inhibition observed in buffer without added Mg2+. Ethanol did not alter [Ca2+]i prior to NMDA addition. In the absence of Mg2+, 50 and 100 mM ethanol did not significantly alter the EC50 value for NMDA, but did inhibit NMDA-induced increases in [Ca2+]i in a concentration-dependent manner at 4, 16, 64, and 256-mu-M NMDA. Whereas NMDA-induced increases in [Ca2+]i were dependent on extracellular Ca2+ and were inhibited by Mg2+, the ability of 100 mM ethanol to inhibit 25 mu-M NMDA responses was independent of the external Ca2+ or Mg2+ concentrations. Glycine (1, 10, and 100-mu-M) enhanced 25-mu-M NMDA-induced increases in [Ca2+]i by approximately 50%. Glycine (1-100-mu-M) prevented the 100 mM ethanol inhibition of NMDA-stimulated [Ca2+]i observed in the absence of exogenous glycine. MK-801 (25-400 nM) inhibited 25-mu-M NMDA-stimulated rises in [Ca2+]i in a concentration-dependent manner. Unlike the additive inhibition observed with Mg2+ plus ethanol, as the concentration of MK-801 increased above 50 nM, ethanol (at 100 mM) did not produce further inhibition of NMDA responses compared with MK-801 alone. These results suggest that ethanol may produce a noncompetitive inhibition of NMDA-stimulated Ca2+ influx in dissociated brain cells, with interactions at the glycine and possibly the phencyclidine site on the NMDA-receptor complex.
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收藏
页码:1536 / 1543
页数:8
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