Nitric oxide synthase containing neurons in the cardiac ganglia of the guinea pig.

应用免疫电镜观察豚鼠心脏一氧化氮合酶（NOS）的免疫反应性。靠近肺静脉开口的许多圆形心内神经节含有nos免疫反应神经元。少数神经元具有免疫反应性，但大部分非免疫反应性神经元被免疫反应性轴突包围。观察到从nos免疫反应性轴突静脉曲张到心内神经节神经元的直接轴-体或脊髓突触。房室结附近的房间隔内可见许多小神经节。这些神经节中的少数神经元也有免疫反应。淋巴结附近或淋巴结内的神经束可见NOS免疫反应轴突。在传导组织和普通心肌之间发现了直径为8-10微米的极厚的免疫反应轴突。电镜检查证实这些轴突无髓鞘。该区域的神经束包含有髓和无髓轴突；然而，免疫反应性仅在无髓鞘轴突中检测到。细小的nos免疫反应性神经纤维终末静脉曲张常见于房室结。nos -免疫反应性轴突静脉曲张与特化心肌细胞密切相关。这些结果表明，一氧化氮可能通过直接的神经肌肉接触在心脏传导组织的神经控制中发挥作用。

Immunoelectron microscopy was performed to localize immunoreactivity for nitric oxide synthase (NOS) in guinea pig heart. Many round intracardiac ganglia, close to the openings of the pulmonary veins, contained NOS-immunoreactive neurons. A small number of neurons were immunoreactive, but most of the non-immunoreactive neurons were surrounded by immunoreactive axons. Direct axo-somatic or-spinic synapses from NOS-immunoreactive axon varicosities to intracardiac ganglionic neurons were observed. Many small ganglia were found in the interatrial septum near the atrioventricular node. A small number of neurons in these ganglia were also immunoreactive. NOS immunoreactive axons were observed in nerve bundles near or within the node. Very thick immunoreactive axons, 8-10 mum in diameter, were found between the conductive tissue and the ordinary cardiac muscles. Electron-microscopic examination confirmed that these axons were unmyelinated. Nerve bundles in this region contained both myelinated and unmyelinated axons ; however, immunoreactivity was detected exclusively in unmyelinated axons. Fine NOS-immunoreactive nerve fibers with terminal varicosities were often seen in the atrioventricular node. Close contact between NOS-immunoreactive axon varicosity and specialized cardiac muscle cell was observed. These results indicate a possibility that nitric oxide plays a role in the neural control of the conductive tissue in the heart through direct neuromuscular contact.