Yamada Y, Tsukamoto G, Kobashi M, Sasaki A, Matsumura T
Department of Oral and Maxillofacial Surgery II, Okayama University Dental School, Japan.
Auton Neurosci. 2000 Sep 1;83(1-2):29-36. doi: 10.1016/S0165-1838(00)00105-3.
The mechanism of induction of emesis by X-ray irradiation remains largely unknown. The purpose of the present research was to clarify the neuronal basis of the induction of nausea induced by X-ray irradiation analyzing c-Fos expression in the nucleus tractus solitarii (NTS) as a marker of cellular excitation. We confirmed that the dose of X-ray irradiation (4 Gy) used for the present research could actually induce nausea by preliminary measurement of kaolin intake. Induction of c-Fos immunoreactivity in the NTS was observed in the animals that received X-ray irradiation of the whole body. The mean number of c-Fos positive cells in the animals that received irradiation was significantly larger than that in the non-irradiated animals. Partial exposure of the abdomen to X-rays showed significantly greater c-Fos expression than that of the head. These results indicated the presence of a certain route for transmitting information from the periphery toward the central nervous system by X-ray irradiation. The number of c-Fos positive cells induced by X-ray irradiation in animals vagotomized at the subdiaphragmatic level was lower than that in sham-operated animals. Animals receiving a serotonin subtype three (5-HT3, 5-hydroxytryptamine) receptor antagonist (tropisetron, ICS 205-930, 3-tropanyl-indole-3-carboxylate) showed a significant reduction in c-Fos protein expression compared to animals receiving a vehicle. These results strongly suggested that X-ray irradiation activates 5-HT3 receptors on the terminals of the abdominal vagal nerves to excite the afferent pathway, thereby inducing emesis.
X射线照射诱发呕吐的机制在很大程度上仍不清楚。本研究的目的是通过分析孤束核（NTS）中c-Fos的表达作为细胞兴奋的标志物，来阐明X射线照射诱发恶心的神经基础。通过初步测量高岭土摄入量，我们证实了本研究中使用的X射线照射剂量（4 Gy）确实能诱发恶心。在接受全身X射线照射的动物中观察到NTS中c-Fos免疫反应性的诱导。接受照射的动物中c-Fos阳性细胞的平均数量显著多于未照射的动物。腹部局部暴露于X射线下显示出比头部更大的c-Fos表达。这些结果表明存在一条通过X射线照射将信息从外周传递到中枢神经系统的特定途径。在膈下水平切断迷走神经的动物中,由X射线照射诱导的c-Fos阳性细胞数量低于假手术动物。与接受赋形剂的动物相比，接受5-羟色胺3型（5-HT3）受体拮抗剂（托烷司琼，ICS 205-930，3-托烷吲哚-3-羧酸酯）的动物c-Fos蛋白表达显著降低。这些结果强烈表明，X射线照射激活腹部迷走神经终末上的5-HT3受体以兴奋传入通路，从而诱发呕吐。
