"Green odor" inhalation by rats down-regulates stress-induced increases in Fos expression in stress-related forebrain regions.
In the present study, on rats, a quantitative analysis of Fos protein immunohistochemistry was performed as a way of investigating the effects of inhalation of green odor (a mixture of equal amounts of trans-2-hexenal and cis-3-hexenol) on the neuronal activations in stress-related forebrain regions induced by acute and repeated stress. Rats were exposed to restraint stress for 90 min each day for 1, 2, 4, 7, or 11 consecutive days. The hypothalamic paraventricular nucleus (PVN), amygdala, hippocampus and paraventricular thalamic nucleus (PVT) were examined. Both acute and repeated restraint stress increased Fos-positive cells in the entire hypothalamic PVN, in the central and medial amygdala, and in PVT, although these responses declined upon repeated exposure to such stress. The stress-induced Fos responses were much weaker in rats that inhaled green odor during each day's restraint. No increases in Fos-positive cells were observed in the hippocampus in acutely stressed rats. The Fos-immunoreactive response to acute stress shown by the piriform cortex did not differ significantly between the vehicle+stress and green+stress groups. Green odor had inhibitory effects on the stress-induced corticosterone response, body-weight loss, and adrenal hypertrophy. These results suggest that in rats, green odor inhalation may, in an as yet unknown way, act on the brain to suppress activity in the neuronal networks involved in stress-related responses (such as activation of the hypothalamo-pituitary-adrenocortical axis and activation of the sympathetic nervous system, as well as stress-induced fear responses).
Ito
Ai
A
Division of Integrative Physiology, Department of Functional, Morphological and Regulatory Science, Tottori University Faculty of Medicine, 86 NIshi-cho, Yonago, Tottori 683, Japan.
Miyoshi
Michio
M
Ueki
Shiori
S
Fukada
Mika
M
Komaki
Ryoichi
R
Watanabe
Tatsuo
T
D000280:Administration, Inhalation; D000447:Aldehydes / Q000494:pharmacology; D000679:Amygdala / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002452:Cell Count; D003345:Corticosterone / Q000378:metabolism; D004195:Disease Models, Animal; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D005239:Fear / Q000187:drug effects / Q000502:physiology; D000441:Hexanols / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology; D008297:Male; D020644:Midline Thalamic Nuclei / Q000187:drug effects / Q000378:metabolism; D009812:Odorants; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects / Q000378:metabolism; D010913:Pituitary-Adrenal System / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D016548:Prosencephalon / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology; D016760:Proto-Oncogene Proteins c-fos / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012149:Restraint, Physical / Q000009:adverse effects; D012903:Smell / Q000187:drug effects* / Q000502:physiology; D013315:Stress, Psychological / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D015431:Weight Loss / Q000187:drug effects / Q000502:physiology
D000447:Aldehydes; D015415:Biomarkers; D000441:Hexanols; D016760:Proto-Oncogene Proteins c-fos; C051918:3-hexen-1-ol; C051750:2-hexenal; D003345:Corticosterone