Hu X J, Ticku M K
Department of Pharmacology, University of Texas Health Science Center, San Antonio 78284, USA.
Brain Res Mol Brain Res. 1995 Jun;30(2):347-56. doi: 10.1016/0169-328x(95)00019-o.
In the present study, we investigated the effects of chronic ethanol exposure on NMDA-mediated increase in intracellular calcium concentration ([Ca2+]i) by means of fluorescent measurement of [Ca2+]i with Fura-2AM in mammalian cortical cultured neurons, and the radioligand [3H]MK-801 binding to cortical neuronal membranes. Chronic exposure of the cortical neurons to ethanol (50 mM, 5 days) did not produce any change in the cell protein, morphological appearance, and the resting [Ca2+]i; however, it significantly enhanced the NMDA-mediated increase in [Ca2+]i. The EC50 value of NMDA was not significantly altered following chronic ethanol exposure, however, its Emax value was increased by approximately 45%. Furthermore, chronic ethanol exposure increased the specific [3H]MK-801 binding in cortical neuronal membrane preparation by approximately 30%. The enhancement of the NMDA-mediated increase in [Ca2+]i and the increase in [3H]MK-801 specific binding were reversed following 48 h ethanol withdrawal. Additionally, this enhanced NMDA response and the increased [3H]MK-801 specific binding were susceptible to blockade by the concomitant chronic exposure of the cortical neurons to the NMDA receptor competitive (20 microM CPP), and non-competitive (1 microM MK-801) antagonists, but not by the non-NMDA receptor antagonist, CNQX (10 microM), and the L-type calcium channel blocker, nitrendipine (10 microM). Taken together, these results suggest that chronic ethanol exposure upregulated the NMDA receptor function and binding in cortical cultured neurons, and this increased NMDA receptor function is a NMDA receptor-mediated process. This altered NMDA receptor function may be responsible for the chronic ethanol-induced behavioral consequences and withdrawal syndrome associated with chronic ethanol exposure.
在本研究中，我们通过用Fura - 2AM荧光测量哺乳动物皮质培养神经元细胞内钙浓度（[Ca2+]i）以及放射性配体[3H]MK - 801与皮质神经元膜结合的方法，研究了慢性乙醇暴露对NMDA介导的细胞内钙浓度升高的影响。将皮质神经元慢性暴露于乙醇（50 mM，5天）对细胞蛋白、形态外观和静息[Ca2+]i没有产生任何变化；然而，它显著增强了NMDA介导的[Ca2+]i升高。慢性乙醇暴露后，NMDA的EC50值没有显著改变，但其Emax值增加了约45%。此外，慢性乙醇暴露使皮质神经元膜制剂中[3H]MK - 801的特异性结合增加了约30%。在乙醇戒断48小时后，NMDA介导的[Ca2+]i升高的增强以及[3H]MK - 801特异性结合的增加被逆转。此外，这种增强的NMDA反应和增加的[3H]MK - 801特异性结合易受皮质神经元同时慢性暴露于NMDA受体竞争性拮抗剂（20 microM CPP）和非竞争性拮抗剂（1 microM MK - 801）的阻断，但不受非NMDA受体拮抗剂CNQX（10 microM）和L型钙通道阻滞剂尼群地平（10 microM）的阻断。综上所述，这些结果表明，慢性乙醇暴露上调了皮质培养神经元中NMDA受体的功能和结合，并且这种增加的NMDA受体功能是一个由NMDA受体介导的过程。这种改变的NMDA受体功能可能是慢性乙醇诱导的行为后果以及与慢性乙醇暴露相关的戒断综合征的原因。
