Sastry B V
Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee.
J Ocul Pharmacol. 1985 Summer;1(2):201-26. doi: 10.1089/jop.1985.1.201.
Acetylcholine (ACh), choline acetyltransferases and cholinesterases occur in cornea, iris-ciliary body complex and retina of several vertebrates. In cornea, ACh may serve as a sensory transmitter as well as a local hormone, the function of which is not delineated. The function of ACh as the parasympathetic neurotransmitter at the iris and ciliary body is well established. The muscarinic receptors on the iris smooth muscle are similar to the muscarinic receptors (M2 type in two way classification) at other smooth muscles towards their interaction with agonists and antagonists. Binding studies using radiolabeled antagonists and their displacement by agonists indicate that muscarinic receptors in membranes of iris-ciliary body complex are heterogeneous indicating more than one subtype of muscarinic receptors. A subtype other than M2 receptors may occur at the presynaptic sites of parasympathetic nerves, which have yet to be investigated using specific agonists and antagonists. Cholinergic markers, choline acetyltransferase and acetylcholinesterase, differ quantitatively and qualitatively in retinas of different species. However, amacrine cells are cholinergic in all vertebrate species. Although they make up 1% of retinal neurons, they influence the activity of a majority of ganglion cells. Cholinergic effects in ganglia are mediated through nicotinic and muscarinic receptors. Both of these types of cholinergic receptors are heterogeneous. They have yet to be investigated for their subtypes using specific agonists and antagonists. Although the role of cholinergic retinal neurons in the processing of visual information is not known, their input to ganglion cells generally increases the rate of spontaneous activity or the number of action potentials in light-evoked responses. Thus, the cholinergic input seems to modify the overall neuronal input to the ganglion cells from the receptive fields. Endothelial cells of blood vessels contain muscarinic receptors, which are activated by ACh to cause relaxation. Although retinal blood vessels provide recognizable characteristic signs in diabetes mellitus and hypertensive disease, no information is available on the muscarinic receptors of these vessels.
乙酰胆碱（ACh）、胆碱乙酰转移酶和胆碱酯酶存在于多种脊椎动物的角膜、虹膜 - 睫状体复合体和视网膜中。在角膜中，ACh可能作为感觉递质以及局部激素发挥作用，但其功能尚未明确。ACh作为虹膜和睫状体处副交感神经递质的功能已得到充分证实。虹膜平滑肌上的毒蕈碱受体与其他平滑肌上的毒蕈碱受体（双向分类中的M2型）在与激动剂和拮抗剂的相互作用方面相似。使用放射性标记拮抗剂的结合研究以及激动剂对其的置换表明，虹膜 - 睫状体复合体膜中的毒蕈碱受体具有异质性，这表明存在不止一种毒蕈碱受体亚型。除M2受体外的一种亚型可能存在于副交感神经的突触前部位，这一点尚未使用特异性激动剂和拮抗剂进行研究。胆碱能标记物胆碱乙酰转移酶和乙酰胆碱酯酶在不同物种的视网膜中在数量和质量上存在差异。然而，无长突细胞在所有脊椎动物物种中都是胆碱能的。尽管它们仅占视网膜神经元的1%，但它们会影响大多数神经节细胞的活性。神经节中的胆碱能效应是通过烟碱型和毒蕈碱型受体介导的。这两种类型的胆碱能受体都是异质性的。尚未使用特异性激动剂和拮抗剂对它们的亚型进行研究。尽管胆碱能视网膜神经元在视觉信息处理中的作用尚不清楚，但它们对神经节细胞的输入通常会增加自发活动的速率或光诱发反应中的动作电位数量。因此，胆碱能输入似乎会改变来自感受野的对神经节细胞的整体神经元输入。血管内皮细胞含有毒蕈碱受体，ACh可激活这些受体导致血管舒张。尽管视网膜血管在糖尿病和高血压疾病中呈现出可识别的特征性迹象，但关于这些血管的毒蕈碱受体尚无相关信息。
