Effects of c -Fos Immunoreactivity on Central Nervous System after Administration of Aspirin

Son, Chang Mok; Kim, Chul Hong; Yoo, Ki Soo

Abstract

Aspirin is one of the popular non -steroid anti -inflammatory drugs used in the management of pain. This study was performed to investigate the effects of aspirin on c -Fos expression in rat CNS after inducing somatic pain with formalin. Male S.D. rats were injected subcutaneously with 0.1 ml of 5% formalin in the plantar surface of right hindpaw. For experimental group, aspirin was administered orally before injection of formalin. Asprin -untreated group was utilized as the control group. Rats were sacrificed at 0.5, 1, 2, 6 and 24 hours after formalin injection. Rat brains were removed and sliced in rat brain matrix. Brain slices were coronally sectioned at interaural 5.70 ~6.70 mm. Serial sections were immunohisto-chemically reacted with polyclonal c -Fos antibody. The numbers of c -Fos protein immunoreactive neurons in the cingulate cortex, primary somatosensory area, and hippocampus were counted and analyzed statistically with Mann - Whitney U test. Results were as follows: 1. Higher numbers of c -Fos immunoreactive neurons were found in the cingulate cortex, primary somatosensory area and hippocampus. 2. Both aspirin -treated and -untreated groups, numbers of c -Fos immunoreactive neurons were significantly higher all time points than formalin -untreated group, which peacked at 2 hours. 3. The numbers of c -Fos immunoreactive neuron of the aspirin -treated group were less compared to the aspirin - untreated group at each time point. In conclusion, these results provide some basic knowledge in understanding the mechanism and control of formalin - induced somatic pain.