Rodríguez M, Mantolán-Sarmiento B, González-Hernández T
Department of Physiology, Faculty of Medicine, University of La Laguna, Tenerife, Spain.
Neuroscience. 1998 Feb;82(3):853-66. doi: 10.1016/s0306-4522(97)00293-5.
The choline analogue, ethylcholine mustard azirinium ion (AF64A), has been proposed as a selective neurotoxin that produces degeneration of central cholinergic neurons. However, the mechanisms of action and the specificity or non-specificity of this toxin are still undefined. In this study, we have investigated the effects of AF64A, in comparison with kainic acid, on cholinergic neurons of the mesopontine formation (pedunculopontine and laterodorsal tegmental nuclei), a neuronal population also expressing nitric oxide synthase, the enzyme responsible for the synthesis of nitric oxide. We used choline acetyltransferase immunohistochemistry as a marker of acetylcholine activity, and nitric oxide synthase immunohistochemistry and NADPH-diaphorase histochemistry as markers of nitric oxide synthase activity. Our results show that the injection of low doses of AF64A produces: (1) an area of cavitation in the injection site of pedunculopontine tegmental nucleus (local non-specific effect), and (2) a transient decrease in choline acetyltransferase immunoreactivity in choline acetyltransferase-nitric oxide synthase neurons in both the ipsilateral laterodorsal tegmental nucleus and the perilesional area of the pedunculopontine tegmental nucleus, while their morphology and nitric oxide synthase immunoreactivity remain unaltered (post-diffusion specific effect). These findings indicate that the loss of choline-related enzymatic activity is not necessarily associated with degeneration of cholinergic neurons, and that the recovery of choline acetyltransferase immunoreactivity may arise from neurons whose activity is diminished during the first postinjection weeks. Taking into account that AF64A is a suitable tool to develop a reversible model of neurological disorders related to cholinergic deficit, further efforts should be directed toward elimination of its local non-specific effect.
胆碱类似物，乙基胆碱氮芥阿齐立宁离子（AF64A），已被提议作为一种选择性神经毒素，可导致中枢胆碱能神经元变性。然而，这种毒素的作用机制以及其特异性或非特异性仍不明确。在本研究中，我们将AF64A与 kainic 酸相比较，研究了其对中脑桥脑结构（脚桥核和外侧背盖核）胆碱能神经元的影响，该神经元群体也表达一氧化氮合酶，即负责合成一氧化氮的酶。我们使用胆碱乙酰转移酶免疫组织化学作为乙酰胆碱活性的标志物，一氧化氮合酶免疫组织化学和NADPH-黄递酶组织化学作为一氧化氮合酶活性的标志物。我们的结果表明，注射低剂量的AF64A会产生：（1）脚桥被盖核注射部位出现空洞区域（局部非特异性效应），以及（2）同侧外侧背盖核和脚桥被盖核损伤周围区域中胆碱乙酰转移酶 - 一氧化氮合酶神经元的胆碱乙酰转移酶免疫反应性短暂降低，而它们的形态和一氧化氮合酶免疫反应性保持不变（扩散后特异性效应）。这些发现表明，胆碱相关酶活性的丧失不一定与胆碱能神经元变性相关，并且胆碱乙酰转移酶免疫反应性的恢复可能源于在注射后的最初几周内活性降低的神经元。考虑到AF64A是建立与胆碱能缺陷相关的神经疾病可逆模型的合适工具，应进一步努力消除其局部非特异性效应。
