title: Head-portion exposure to low-level X-rays reduces isolation-induced aggression of mouse, and involvement of the olfactory carnosine in modulation of the radiation effects.
abstract: Social isolation has been widely described to induce a compulsive aggressive behavior. The aggressiveness due to isolation in mice has often been used as a means for the better understanding of disturbed behavior in human beings. In the course of a study of the behavioral effects, we have noticed that fighting injuries, usually observed among male ICR mice, tend to decrease in mice irradiated with low-dose X-rays. We, therefore, quantitatively examined the effects of low-dose X-irradiation on aggressive behavior using a resident-intruder paradigm in which a resident mouse attacks an intruder that entered its territory. Male ICR white Swiss mice became gradually calm, and showed remarkably quiet behavior 7-10 days after whole-head 5 or 15 cGy X-irradiation. Only exposure of the anterior part of the head (olfactory system including orbits) also induced the remarkable suppression of the aggressive behavior. The olfactory system has direct access to the limbic system, a central part of the brain concerned with emotion. The calm behavior induced by low-dose X-irradiation might be related to the changes in the olfactory function. We also obtained data on brain biochemistry giving further support for the above low-dose effects on mouse behavior. The carnosine content and its synthetase activity in the olfactory bulbs decreased significantly after only the anterior part of the head had been exposed. Higher doses (25-35 cGy), however, did not induce such effects. The results suggest that the depression of aggressive behavior is limited to animals irradiated with the smaller doses.
authors.affiliation: Department of Physiology, Toho University School of Medicine, Tokyo, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Miyachi
authors.forename: T
authors.initials: T
authors.lastname: Yamada
mesh_terms: D000374:Aggression / Q000528:radiation effects*; D000818:Animals; D002336:Carnosine / Q000502:physiology*; D004307:Dose-Response Relationship, Radiation; D006257:Head / Q000528:radiation effects*; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D009830:Olfactory Bulb / Q000201:enzymology / Q000528:radiation effects; D010453:Peptide Synthases / Q000378:metabolism; D012903:Smell / Q000528:radiation effects*; D012934:Social Isolation; D014965:X-Rays; D019287:Zinc Sulfate / Q000494:pharmacology
chemical_list: D019287:Zinc Sulfate; D002336:Carnosine; D010453:Peptide Synthases; C019844:carnosine synthetase