The Changes of c-fos and c-jun after Capsaicine Treatment in the Rat Brain

Park, Gyung Ah; Lee, Jong Eun; Park, Seung Hwa; Jang, Sang Ho; Lee, Won Taek

Abstract

The expression of c-fos and c-jun in the brain of the rat after capsaicin treatment was investigated by in situ hybridization, dot blot hybridization and immunocytochemical methods. Adult male Sprague-Dawley rats[200g] were used for this study. The first set of rats received a single subcutaneous injection of capsaicin[50mg/Kg] dissolved in 10% Tween-80 and 10% ethanol in saline. The rats were decapitated 1, 3, 5, 10, 24, 72 hours and 1 week after capsaicin treatment. The control set of rats were treated with saline instead of capsaicin. In situ hybridization and dot blot hybridization were carried out. O1igonucleotide probe complimentary to c-fos mRNA sequences were used for this study and labeling of oligonucleotides was accomplished using the DNA tailing kit. The expression of c-fos mRNA on the nucleus of neurons in in situ hybridization was observed throughout the brain, and was especially abundant in the olfactory cortex, nucleus of diagonal band of Broca, habenular nuclei, periaqueductal gray, parabrachial nucleus, entopeduncular nucleus, ventral posterolateral nucleus of the thalamus and cerebellum. Compared to the control rats, c-fos mRNA were increased 24 hours after capsaicin injection and gradually decreased after 72 hours, returning to the normal control level 1 week after capsaicin injection. c-fos mRNA was detected only 1 week after capsaicin injection in the various areas of the brain. The fos protein-like immunoreactivity was initially somewhat decreased at 24 hours, but increased at 72 hours and reactions was maximally observed at 1 week after capsaicin treatment. But Jun protein immunoreactivity was not increased, on the contrary, it was even decreased both in numbers of reactive cells and immunoreactivity 1 week after capsaicin injection. From the above results, c-fos gene expression was pronounced in the nucleus concerned with pain, olfaction and taste such as VPL nucleus of the thalamus, olfactory cortex and parabrachial nucleus, in the limbic system concerned with stress and emotion such as nucleus of diagonal band of Broca, periaqueductal gray and habenular nucleus, in the structure concerned with somatic motor function such as entopeduncular nucleus and cerebellum. Also, the c-fos gene was activated by the capsaicin early in the course of effects, then the fos protein increased as a results of c-fos activation. On the other hand, c-jun did not respond to capsaicin treatment early in the course, but Jun protein decreased late in the course of capsaicin effects.