All issues > Volume 46(7); 2003

Original Article

J Korean Pediatr Soc. 2003;46(7):695-701. Published online July 15, 2003.

Changes of c-Fos Immunoreactivity in Midbrain by Deep Pain and Effects of Aspirin

Jin A JA Jung¹, Ki Soo KS Yoo², Kyu Keun KK Hwang¹

¹Department of Pediatrics, College of Medicine, Dong-A University, Busan, Korea
²Department of Anatomy, College of Medicine, Dong-A University, Busan, Korea

Abstract

Purpose
: It had been suggested that pain arising from deep somatic body regions influences neural activity within periaqueductal gray(PAG) of midbrain via distinct spinal pathways. Aspirin is one of the popular non-steroidal anti-inflammatory drugs used in the management of pain. Fos expression was used as a marker for neuronal activity throughout central neurons following painful peripheral stimulation. This study was prepared to investigate changes of c-Fos immunoreactivity in midbrain by deep pain and effects of aspirin.
Methods
: Male Sprague-Dawley rats were injected with 0.1 mL of 5% formalin in the plantar muscle of the right hindpaw. For experimental group II, aspirin was injected intravenously before injection of formalin. An aspirin-untreated group was utilized as group I. Rats were sacrificed at 0.5, 1, 2, 6 and 24 hours after formalin injection. Rat's brains were removed and sliced in rat brain matrix. Brain slices were coronally sectioned at interaural 1.00-1.36 mm. Serial sections were immunohistochemically reacted with polyclonal c-Fos antibody. The numbers of c-Fos protein immunoreactive neurons in ventrolateral periaqueductal gray(VLPAG) and dorsomedial periaqueductal gray(DMPAG) were counted and analyzed statistically with Mann-Whitney U tests.
Results
: Higher numbers of c-Fos protein immunoreactive neurons were found in VLPAG. In both VLPAG and DMPAG of formalin-treated group, the numbers of c-Fos protein immunoreactive neurons were significantly higher at all time points than the formalin-untreated group, which peaked at two hours. The numbers of c-Fos immunoreactive neuron of the aspirin-treated group were less compared to the aspirin-untreated group at each time point.
Conclusion
: These results provide some basic knowledge in understanding the mechanism of formalin-induced deep somatic pain and the effects of aspirin.

Keywords :Aspirin, Pain, Formalin, c-Fos, PAG