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To assess changes in natural killer cell activity and the number of c-Fos-positive cells in hypothalamic structures induced by painful electrical stimulation and to use extremely high frequency irradiation of the skin to modulate these processes.
Experiments were performed on rats subjected to painful electrical stimulation of the hind limbs combined with extremely high frequency irradiation of the skin.
ばく露時間: continuous, twice 40 min exposures with 40 min pause between them
The stress model was based on electrical pain stimulation which was carried out by applying 2.5 mA shocks of 1 s duration with a mean of 10 impulses/ min for a period of 40 min by clasping the electrodes tightly to the rats ankles. The pain stimulation was given either before or after the exposure or applied alone.
|ばく露時間||continuous, twice 40 min exposures with 40 min pause between them|
|ばく露装置の詳細||Rats placed into a cylindrical plastic container; their skin was exposed in the following three places: both shins (hind legs) 3 mm below and 3 mm lateral to the center of the knee and the back of the neck between the seventh cervical and the first thoracic vertebrae along the mid line.|
|Sham exposure||A sham exposure was conducted.|
Painful electric stimulation was associated with a significant decrease in splenic natural killer cell cytotoxicity and a dramatic increase in c-Fos-positive cell counts in some hypothalamic structures. Two irradiations, one before and one after electric stimulation, prevented the decrease of natural killer cell activity and caused a reduction in the number of c-Fos-positive cells expressed in one hypothalamic nucleus and a specific hypothalamic area. Negative correlation was found between c-Fos-positive cell counts in one hypothalamic nucleus/a specific hypothalamic area and the cytotoxic activity of natural killer cells.
The data suggest that painful electric stimulation of the hind limbs of rats causes a reorganization of the central mechanism regulating splenic natural killer cell activity resulting in a decrease in their cytotoxicity, and that extremely high frequency exposure of the skin prevents this reorganization, thus protecting splenic natural killer cell activity from the impairment induced by the painful electric stimulation.