Meriney S D, Pilar G
Department of Physiology and Neurobiology, University of Connecticut, Storrs 06268.
J Neurosci. 1987 Dec;7(12):3827-39. doi: 10.1523/JNEUROSCI.07-12-03827.1987.
The mechanical and pharmacological characteristics of the cholinergic activation of the smooth muscle in the choroidal coat of the chick eye have been assessed in tissues isolated from birds 1 d posthatching using histological, electrophysiological, and immunological techniques. The choroidal coat is innervated by a dense network of cholinergic nerves that make en passant synapses with smooth muscle. Thirty-hertz stimulation of these nerves initiates red blood cell (RBC) movement in the vessels of the choroidal coat, and this activation is blocked by muscarinic ACh receptor (AChR) antagonists. Force-transducer recordings of nerve-induced contractions of this tissue have a slow onset and relaxation time course similar to those of smooth muscle contractions. Furthermore, since nearly half the cholinergic neurons innervating the choroid die within a defined period during development, the onset and pharmacology of this innervation were studied during embryogenesis. With a neural cytoskeletal-like immunostain, we demonstrated that choroid axons are present in peripheral tissue by stage (St) 29. Extracellular electrical recordings made after choroid nerve stimulation allowed us to distinguish axon from muscle responses. These procedures permitted us to examine the time course of the innervation of the smooth muscle. However, to visualize the postsynaptic smooth muscle response, it was necessary to treat the isolated preparation with tetraethylammonium chloride (TEA). Accordingly, TEA-enhanced electrical smooth muscle responses to single-nerve stimuli could be recorded only after St 39. Treatment of the nerve-muscle preparation with prostigmine allowed the recording of TEA-enhanced electrical activity as early as St 36 (1 d after the beginning of the normal choroid neuron death period). This synaptic activation was completely blocked by atropine or quinuclidinyl benzylate (QNB), and was not affected by alpha bungarotoxin (alpha BTX), indicating that, as in the posthatching tissue, neuromuscular transmission is mediated by muscarinic receptors. These results show that cholinergic muscarinic activation of the choroidal coat can occur as early as St 36, but that it is not as efficient as transmission later in embryogenesis.
利用组织学、电生理学和免疫学技术，对孵化后1天的雏鸡眼部脉络膜层平滑肌胆碱能激活的机械和药理学特性进行了评估。脉络膜层由密集的胆碱能神经网络支配，这些神经与平滑肌形成旁突触。对这些神经进行30赫兹的刺激会引发脉络膜层血管中的红细胞（RBC）运动，这种激活会被毒蕈碱型乙酰胆碱受体（AChR）拮抗剂阻断。该组织神经诱导收缩的力传感器记录显示，其起始和松弛时间进程与平滑肌收缩相似。此外，由于支配脉络膜的胆碱能神经元在发育过程中的特定时期内近一半会死亡，因此在胚胎发生过程中研究了这种神经支配的起始和药理学特性。通过神经细胞骨架样免疫染色，我们证明在第29阶段（St）外周组织中已存在脉络膜轴突。脉络膜神经刺激后的细胞外电记录使我们能够区分轴突反应和肌肉反应。这些方法使我们能够研究平滑肌神经支配的时间进程。然而，为了观察突触后平滑肌反应，有必要用氯化四乙铵（TEA）处理分离的标本。因此，只有在第39阶段之后才能记录到TEA增强的平滑肌对单神经刺激的电反应。早在第36阶段（正常脉络膜神经元死亡期开始后1天），用新斯的明处理神经-肌肉标本就可以记录到TEA增强的电活动。这种突触激活被阿托品或喹核苄酯（QNB）完全阻断，而不受α-银环蛇毒素（αBTX）影响，这表明，与孵化后组织一样，神经肌肉传递由毒蕈碱受体介导。这些结果表明，脉络膜层的胆碱能毒蕈碱激活最早可在第36阶段发生，但不如胚胎发育后期的传递有效。
