Loring R H, Aizenman E, Lipton S A, Zigmond R E
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts.
J Neurosci. 1989 Jul;9(7):2423-31. doi: 10.1523/JNEUROSCI.09-07-02423.1989.
Nicotinic receptor function has been described in the retinas of a variety of vertebrate species. Neuronal bungarotoxin (NBT, also known as bungarotoxin 3.1, toxin F, or kappa-bungarotoxin) blocks nicotinic receptors in several neuronal preparations, while the neuromuscular antagonist alpha-bungarotoxin (BGT) fails to block most of these receptors. NBT (100 nM), but not BGT (10 microM), substantially blocks nicotinic function on ganglion cells in intact chick retina. 125I-NBT binds to 2 sites in homogenates of chick retina; one site that is shared with BGT (Kd = 5-7 nM, Bmax approximately 500 fmol/retina) and one which is not (Kd = 2-3 nM, Bmax approximately 100 fmol/retina). 125I-NBT binding to the NBT-specific site (binding in the presence of 1 microM unlabeled BGT) is localized to 2 bands in the inner plexiform layer, corresponding to regions richly innervated by neurons containing immunoreactivity for choline acetyltransferase. Furthermore, this binding is blocked by competitive nicotinic agonists and antagonists, but nicotine or other nicotinic agonists do not displace 125I-NBT binding with very high affinity relative to the displacement of 3H-nicotine reported by others in brain. Thus, of the 2 NBT binding sites, the site not recognized by BGT most likely represents functional nicotinic receptors in the chick retina, but these receptors have relatively low affinity for nicotinic agonists, similar to nicotinic receptors found in autonomic ganglia.
在多种脊椎动物的视网膜中，已对烟碱型受体的功能进行了描述。神经元型银环蛇毒素（NBT，也称为银环蛇毒素3.1、毒素F或κ-银环蛇毒素）可阻断多种神经元制剂中的烟碱型受体，而神经肌肉拮抗剂α-银环蛇毒素（BGT）则无法阻断这些受体中的大多数。NBT（100 nM）而非BGT（10 μM）可显著阻断完整鸡视网膜中神经节细胞的烟碱型功能。125I-NBT与鸡视网膜匀浆中的2个位点结合；一个位点与BGT共有（解离常数Kd = 5 - 7 nM，最大结合量Bmax约为500 fmol/视网膜），另一个则不与BGT共有（Kd = 2 - 3 nM，Bmax约为100 fmol/视网膜）。125I-NBT与NBT特异性位点的结合（在1 μM未标记BGT存在下的结合）定位于内网状层的2条带，对应于富含对胆碱乙酰转移酶具有免疫反应性的神经元大量支配的区域。此外，这种结合可被竞争性烟碱型激动剂和拮抗剂阻断，但相对于其他人在脑中报道的3H-尼古丁的置换，尼古丁或其他烟碱型激动剂并不能以非常高的亲和力置换125I-NBT的结合。因此，在这2个NBT结合位点中，不被BGT识别的位点很可能代表鸡视网膜中的功能性烟碱型受体，但这些受体对烟碱型激动剂的亲和力相对较低，类似于在自主神经节中发现的烟碱型受体。
