Open-channel blockade is less effective on GluN3B than GluN3A subunit-containing NMDA receptors

详细信息	查看全文 | 推荐本文 |

• 作者：David W. McClymont^a ; ¹ ; John Harris^b ; Ian R. Mellor^a ; ^{ian.mellor@nottingham.ac.uk}
• 关键词：N-methyl-d-aspartate receptors ; GluN3 subunit ; Channel block ; Magnesium ; Memantine ; MK-801 ; Philanthotoxin-343 ; Methoctramine
• 刊名：European Journal of Pharmacology
• 出版年：2012
• 期刊代码：24_00142999
• 类别：neu
• 出版时间：5 July, 2012
• 卷：686
• 期：1-3
• 页码：22-31
• 文件大小：1509 K

摘要

The GluN3 subunits of the N-methyl-d-aspartate (NMDA) receptor are known to reduce its Ca²⁺ permeability and Mg²⁺ sensitivity, however, little is known about their effects on other channel blockers. cRNAs for rat NMDA receptor subunits were injected into Xenopus oocytes and responses to NMDA and glycine were recorded using two electrode voltage clamp. Channel block of receptors containing GluN1-1a/2A, GluN1-1a/2A/3A or GluN1-1a/2A/3B subunits was characterised using Mg²⁺, memantine, MK-801, philanthotoxin-343 and methoctramine. IC₅₀ values for Mg²⁺ and memantine increased when receptors contained GluN3A subunits and were further increased when they contained GluN3B, e.g. IC₅₀s at 鈭?#xA0;75 mV for block of GluN1-1a/2A, GluN1-1a/2A/3A and GluN1-1a/2A/3B receptors respectively were 4.2, 22.4 and 40.1 渭M for Mg²⁺, and 2.5, 7.5 and 17.5 渭M for memantine. Blocking activity was found to be fully or partially restored when G or R (at the N and N + 1 sites respectively) were mutated to N in GluN3A. Thus, the changes cannot be attributed to the loss of the N or N + 1 sites alone, but rather involve both sites or residues elsewhere. Block by MK-801 and philanthotoxin-343 was also reduced by GluN3A, most strongly at 鈭?#xA0;100 mV but not at 鈭?#xA0;50 mV, and by GluN3B at all V_h. Methoctramine was the least sensitive to introduction of GluN3 subunits suggesting a minimal interaction with the N and N + 1 sites. We conclude that GluN3B-containing receptors provide increased resistance to channel block compared to GluN3A-containing receptors and this must be due to differences outside the deep pore region (N site and deeper).