Department of Pharmacology, Israel Institute for Biological Research, P.O. Box 19, Ness Ziona, 74100, Israel.
Department of Pharmacology, Israel Institute for Biological Research, P.O. Box 19, Ness Ziona, 74100, Israel.
Neurotoxicology. 2018 Mar;65:248-254. doi: 10.1016/j.neuro.2017.11.002. Epub 2017 Nov 8.
The effect of sarin on the binding parameters (KD & Bmax) of M2 muscarinic acetylcholine receptor (mAChR) was studied 24h and 1 week post exposure. Male & female Sprague-Daweley rats were poisoned with 1XLD50 sarin (80μg/kg, im) followed by treatment of trimedoxime bromide and atropine (7.5:5mg/kg, im) 1min later. Brains were removed and analyzed for M2 mAChR binding, using [H]AFDX384, an M2 selective antagonist. A significant increase in KD of M2 mAChR was found in the cortex 24h post poisoning, displaying elevation from 4.65±1.16 to 8.45±1.06nM and 5.24±0.93 to 9.29±1.56nM in male and female rats, respectively. A rise in KD was also noted 1 week following exposure from 5.04±1.20 to 11.75±2.78 and from 5.37±1.02 to 11.66±1.73nM, presenting an added increase of 51 and 40% (compared to 24h) in males and females, respectively. Analysis of M2 receptor density (Bmax) revealed a significant reduction of 68% in males and insignificant reduction of 22% in females, 24h after sarin exposure which was followed by 37% recovery in males and 100% recovery in females, 1 week later. These results indicate that sarin induces a long-term decreased affinity in M2 mAChR (elevated KDs) and a transient effect on the number of this receptor subtype (Bmax). We hypothesize that the reduced affinity of the M2 receptors (negative auto-regulatory receptors) may cause long-term brain deficits by impairing the normal regulation release of ACh into the synaptic cleft.
研究了沙林暴露 24 小时和 1 周后对 M2 毒蕈碱乙酰胆碱受体（mAChR）结合参数（KD 和 Bmax）的影响。雄性和雌性 Sprague-Daweley 大鼠用 1XLD50 沙林（80μg/kg，im）中毒，1 分钟后用三羟肟溴和阿托品（7.5：5mg/kg，im）治疗。取出大脑并使用 M2 选择性拮抗剂[H]AFDX384 分析 M2 mAChR 结合。中毒后 24 小时发现 M2 mAChR 的 KD 显著增加，雄性和雌性大鼠的 KD 值分别从 4.65±1.16 增加到 8.45±1.06nM 和 5.24±0.93 增加到 9.29±1.56nM。暴露后 1 周时也观察到 KD 升高，从 5.04±1.20 增加到 11.75±2.78 和从 5.37±1.02 增加到 11.66±1.73nM，雄性和雌性分别增加了 51%和 40%（与 24 小时相比）。分析 M2 受体密度（Bmax）显示，沙林暴露 24 小时后雄性大鼠的 M2 受体密度显著减少 68%，而雌性大鼠的 M2 受体密度减少不明显，为 22%，1 周后雄性大鼠的 M2 受体密度恢复 37%，而雌性大鼠的 M2 受体密度完全恢复。这些结果表明，沙林诱导 M2 mAChR 长期亲和力降低（KD 升高）和该受体亚型数量的短暂效应（Bmax）。我们假设，M2 受体（负自动调节受体）亲和力降低可能通过损害 ACh 向突触间隙正常释放来导致长期脑损伤。
