alpha-Melanophore-stimulating hormone (alpha-MSH) antagonizes interleukin-1beta-induced hyperalgesia and Fos expression in the paraventricular and arcuate nucleus of the rat.
It is known that intracerebroventricular (ICV) administration of a low dose of interleukin-1beta (IL-1beta) induces hyperalgesia and that this effect can be inhibited by alpha-melanophore-stimulating hormone (alpha-MSH). To identify the part of the brain that is affected by hyperalgesia-induced IL-1beta and the possible site of alpha-MSH inhibition, we have examined Fos expression in the rat brain in response to ICV microinjection of alpha-MSH and/or IL-1beta. Following injection of 10 pg IL-1beta, hyperalgesia was induced and Fos became expressed in the paraventricular nucleus (PVN) of the hypothalamus and in the arcuate nucleus (ARC), which contains alpha-MSH-producing neurons. IL-1beta injection did not induce Fos expression in the pars intermedia of the pituitary gland, which contains endocrine melanotrope cells that release alpha-MSH into the systemic circulation. ICV co-injection of IL-1beta with 30 ng alpha-MSH fully inhibited both hyperalgesia and Fos expression in the PVN and the ARC. We conclude that PVN neurons are activated by hyperalgesic IL-1beta and propose that this effect is abolished by alpha-MSH possibly released from the ARC but not from the pituitary gland.
Tonosaki
Yoshikazu
Y
Department of Anatomy, Hirosaki University School of Medicine, Hirosaki, Japan. tonosaki@cc.hirosaki-u.ac.jp
Nishiyama
Keiji
K
Roubos
Eric W
EW
Sugiura
Yasuo
Y
D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000378:metabolism*; D006930:Hyperalgesia / Q000378:metabolism*; D007375:Interleukin-1 / Q000008:administration & dosage / Q000502:physiology*; D008297:Male; D008845:Microinjections; D017288:Pain Threshold / Q000502:physiology*; D010286:Paraventricular Hypothalamic Nucleus / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D000521:alpha-MSH / Q000502:physiology*
D007375:Interleukin-1; D016760:Proto-Oncogene Proteins c-fos; D000521:alpha-MSH