Hershkowitz N, Bryan R N
Invest Radiol. 1982 May-Jun;17(3):271-5.
Synaptically evoked extracellular field potentials were obtained from the pyramidal cell layer of the Cal field of rat hippocampus slices. Synaptic activity was evoked by Schaffer's collateral stimulation. The effects of the water-soluble contrast agents Na-diatrizoate and metrizamide, as well as control solutions of NaCl and sucrose, were studied. Test solutions were 300-345 mOsm and had iodine concentrations of 3-30 mg I/ml. The effects of test solutions are apparent within 10 minutes and reversible within 30-45 minutes. Control recordings have a small positive potential, followed by a large negative spike and a final slow positive wave. Contrast agents have two effects. The first is an epileptogenic property characterized by repetitive negative spikes arising from an extended slow positive field. The second effect is a depression characterized by a reduction in the amplitude of the synaptically evoked fields, particularly the negative spikes. Na-diatrizoate predominately produces the first effect, while metrizamide principally produces the second. Hyperosmolar solutions only produce depression. These results correlate well with the clinical setting where Na-diatrizoate is a potent convulsant, while metrizamide produces symptoms compatible with neuronal depression. These results indicate that contrast agent seizure activity is not due to hyperosmolarity but to a more direct chemical effect. The depression, however, may be related to a hyperosmolar effect.
从大鼠海马切片CA1区锥体细胞层记录到突触诱发的细胞外场电位。通过刺激Schaffer侧支诱发突触活动。研究了水溶性造影剂泛影酸钠和甲泛葡胺以及氯化钠和蔗糖对照溶液的作用。测试溶液的渗透压为300 - 345 mOsm，碘浓度为3 - 30 mg I/ml。测试溶液的作用在10分钟内明显，在30 - 45分钟内可逆。对照记录有一个小的正电位，随后是一个大的负峰和最后的缓慢正波。造影剂有两种作用。第一种是致癫痫特性，其特征是在扩展的缓慢正场中出现重复的负峰。第二种作用是抑制，其特征是突触诱发场的幅度降低，特别是负峰。泛影酸钠主要产生第一种作用，而甲泛葡胺主要产生第二种作用。高渗溶液仅产生抑制作用。这些结果与临床情况密切相关，在临床中泛影酸钠是一种强效惊厥剂，而甲泛葡胺产生与神经元抑制相符的症状。这些结果表明，造影剂的癫痫发作活动不是由于高渗性，而是由于更直接的化学作用。然而，抑制作用可能与高渗效应有关。
