Abdominal vagi mediate c-Fos expression induced by X-ray irradiation in the nucleus tractus solitarii of the rat.
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.
Yamada
Y
Y
Department of Oral and Maxillofacial Surgery II, Okayama University Dental School, Japan. yyamada@dent.okayama-u.ac.jp
Tsukamoto
G
G
Kobashi
M
M
Sasaki
A
A
Matsumura
T
T
D000005:Abdomen / Q000294:innervation / Q000503:physiopathology / Q000528:radiation effects*; D000818:Animals; D007211:Indoles / Q000494:pharmacology; D007616:Kaolin / Q000378:metabolism; D008297:Male; D009325:Nausea / Q000209:etiology / Q000473:pathology / Q000503:physiopathology; D009474:Neurons / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011985:Receptors, Serotonin / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects*; D044406:Receptors, Serotonin, 5-HT3; D012702:Serotonin Antagonists / Q000494:pharmacology; D017552:Solitary Nucleus / Q000473:pathology / Q000503:physiopathology / Q000528:radiation effects*; D000077526:Tropisetron; D014630:Vagus Nerve / Q000473:pathology / Q000503:physiopathology / Q000528:radiation effects*; D014839:Vomiting / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology; D014965:X-Rays / Q000009:adverse effects*
D007211:Indoles; D016760:Proto-Oncogene Proteins c-fos; D011985:Receptors, Serotonin; D044406:Receptors, Serotonin, 5-HT3; D012702:Serotonin Antagonists; D007616:Kaolin; D000077526:Tropisetron