PII S0361-9230(97)00277-3 REVIEW ARTICLE Using c-fos as a Neural Marker of Pain

over a decade has past since Hunt et al. [31]. reported that the gene c-fos and its protein product Fos are expressed in the spinal cord of rats subjected to peripheral noxious stimulation. These authors showed that noxious stim-ulation (application of radiant heat or mustard oil) to the hind paw resulted in a massive increase in the expression of Fos in neurons in the dorsal horn of the lumbar spinal cord. Since then, there has been an explosion of studies in which c-fos has been used to study nociception (pain), and the number of such stud-ies increases each year. The net result has been to establish c-fos expression as a valuable tool in pain research. Moreover, recent studies have provided evidence identifying the role of c-fos expression in spinal nociceptive processes. However, there are several important limitations to the practice of using c-fos to study nociception, and these limitations can be easily overlooked as the practice graduates to the status of an estab-lished technique. The increasing use of c-fos to study nocicep-tion necessitates a critical review of the practice, identifying the shortcomings as well as the strengths of this tool. © 199