Assessment of subunit-dependent direct gating and allosteric modulatory effects of carisoprodol at GABA(A) receptors.
Assessment of subunit-dependent direct gating and allosteric modulatory effects of carisoprodol at GABA(A) receptors.
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DOI：
10.1016/j.neuropharm.2015.04.007
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发表时间：
2015-10
影响因子：
4.7
通讯作者：
Dillon GH
中科院分区：
文献类型：
--
作者：
Kumar M;González LA;Dillon GH
卡立普多是一种广泛使用的肌肉松弛剂，近年来滥用情况大大增加。它直接激活和变构调节α1β2γ2 GABAAR，尽管作用位点未知。为了深入了解卡立普多的作用，评估了该药物的亚基依赖性作用。从表达α1β2、α1β3或αxβzγ2（其中x = 1-6和z = 1-3）GABAAR的HEK 293细胞以及包含δ亚基的受体（模拟突触外受体）中获得全细胞膜片钳记录。对于所有配置，都观察到直接门控和变构增强GABA门控电流的能力。存在或不存在γ2亚基不影响卡立普多直接门控或变构调节受体的能力。相对于最大GABA电流，β1亚基的存在赋予直接激活的最高功效，而β2亚基的存在赋予GABA反应的变构调节的最高功效。关于α亚基，卡立普多在增强GABA在整合α1亚基的受体中的作用方面最有效。无论α亚基亚型如何，直接门控受体的能力通常相当，尽管掺入α3亚基的受体显示直接门控功效和亲和力显著降低。在突触外（α1β3δ和α4β3δ）受体中，卡立普多作为直接门控激动剂的疗效高于GABA。此外，卡立普多变构增强这些受体中的EC 20和饱和GABA浓度。在评估电压依赖性时，我们发现直接门控和抑制效应对膜电压不敏感，而别构调节效应受膜电压的影响。我们的研究结果表明，卡立普多在突触和突触外GABAAR的直接和变构作用，亚基亚型影响这些作用。
Carisoprodol is a widely prescribed muscle relaxant, abuse of which has grown considerably in recent years. It directly activates and allosterically modulates α1β2γ2 GABAARs, although the site(s) of action are unknown. To gain insight into the actions of carisoprodol, subunit-dependent effects of this drug were assessed. Whole-cell patch clamp recordings were obtained from HEK293 cells expressing α1β2, α1β3 or αxβzγ2 (where x = 1–6 and z = 1–3) GABAARs, and in receptors incorporating the δ subunit (modeling extrasynaptic receptors). The ability to directly gate and allosterically potentiate GABA-gated currents was observed for all configurations. Presence or absence of the γ2 subunit did not affect the ability of carisoprodol to directly gate or allosterically modulate the receptor. Presence of the β1 subunit conferred highest efficacy for direct activation relative to maximum GABA currents, while presence of the β2 subunit conferred highest efficacy for allosteric modulation of the GABA response. With regard to α subunits, carisoprodol was most efficacious at enhancing the actions of GABA in receptors incorporating the α1 subunit. The ability to directly gate the receptor was generally comparable regardless of the α subunit isoform, although receptors incorporating the α3 subunit showed significantly reduced direct gating efficacy and affinity. In extrasynaptic (α1β3δ and α4β3δ) receptors, carisoprodol had greater efficacy than GABA as a direct gating agonist. In addition, carisoprodol allosterically potentiated both EC20 and saturating GABA concentrations in these receptors. In assessing voltage-dependence, we found direct gating and inhibitory effects were insensitive to membrane voltage, whereas allosteric modulatory effects were affected by membrane voltage. Our findings demonstrate direct and allosteric effects of carisoprodol at synaptic and extrasynpatic GABAARs and that subunit isoform influences these effects.