Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, Canada.
Mol Pain. 2011 Nov 17;7:89. doi: 10.1186/1744-8069-7-89.
Both T-type calcium channels and cannabinoid receptors modulate signalling in the primary afferent pain pathway. Here, we investigate the analgesics activities of a series of novel cannabinoid receptor ligands with T-type calcium channel blocking activity.
Novel compounds were characterized in radioligand binding assays and in vitro functional assays at human and rat CB1 and CB2 receptors. The inhibitory effects of these compounds on transient expressed human T-type calcium channels were examined in tsA-201 cells using standard whole-cell voltage clamp techniques, and their analgesic effects in response to various administration routes (intrathecally, intraplantarly, intraperitoneally) assessed in the formalin model. A series of compounds were synthesized and evaluated for channel and receptor activity. Compound NMP-7 acted as non-selective CB1/CB2 agonist while NMP4 was found to be a CB1 partial agonist and CB2 inverse agonist. Furthermore, NMP-144 behaved as a selective CB2 inverse agonist. All of these three compounds completely inhibited peak Cav3.2 currents with IC50 values in the low micromolar range. All compounds mediated analgesic effects in the formalin model, but depending on the route of administration, could differentially affect phase 1 and phase 2 of the formalin response.
Our results reveal that a set of novel cannabinioid receptor ligands potently inhibit T-type calcium channels and show analgesic effects in vivo. Our findings suggest possible novel means of mediating pain relief through mixed T-type/cannabinoid receptor ligands.
T 型钙通道和大麻素受体都能调节初级传入疼痛通路中的信号转导。在这里，我们研究了一系列具有 T 型钙通道阻断活性的新型大麻素受体配体的镇痛活性。
在放射性配体结合测定和体外功能测定中，对新型化合物进行了鉴定，这些测定是在人源和大鼠 CB1 和 CB2 受体上进行的。使用标准全细胞膜片钳技术，在 tsA-201 细胞中检查了这些化合物对瞬时表达的人 T 型钙通道的抑制作用，并在福尔马林模型中评估了它们通过各种给药途径（鞘内、足底、腹腔内）的镇痛作用。合成了一系列化合物并对其进行了通道和受体活性评估。化合物 NMP-7 表现为非选择性 CB1/CB2 激动剂，而 NMP4 被发现为 CB1 部分激动剂和 CB2 反向激动剂。此外，NMP-144 表现为选择性 CB2 反向激动剂。这三种化合物均完全抑制 Cav3.2 峰值电流，IC50 值在低微摩尔范围内。所有化合物均介导福尔马林模型中的镇痛作用，但根据给药途径的不同，可能会对福尔马林反应的第 1 相和第 2 相产生不同的影响。
我们的结果表明，一组新型大麻素受体配体能够强烈抑制 T 型钙通道，并在体内显示出镇痛作用。我们的研究结果表明，通过混合 T 型/大麻素受体配体可能为缓解疼痛提供新的方法。
