A new experimental model for studies of local inflammatory reactions

The aim of the present study was to develop and evaluate a method for studies of the early phase of the local inflammatory reaction, based on continuous diffusion of an inflammatory inducing agent. 25 rats were used. Four sterile teflon tablets were implanted subcutaneously in the back of each animal. After 3 weeks, when a connective tissue capsula had formed, the tablets were replaced by two test tablets, containing 35 micrograms lipopolysaccaride, one placebo and one teflon tablet. Five rats were sacrificed on day 0, 4, 7, 14, 21, respectively, and biopsies comprising tablet and surrounding tissue were harvested and exposed to routine histologic treatment. The number of leucocytes was assessed in four defined areas adjacent to each tablet. During the first seven days an increase in the number of leucocytes was seen in the tissues adjacent to test tablets. After 14 and 21 days the number of leucocytes was still high but lower as compared to day 7. In the tissues bordering the placebo and teflon tablets only few inflammatory cells were found. The results suggest that the tested method is suitable for studies of local inflammatory reactions during a 21 day period in experimental animals.