Fig. 1. A, Effect of electrical stimulation on BK-induced PE in the rat knee joint. In both groups of rats, baseline PE was established in the first three samples. In one group, BK (150 nm; ○, n = 8) was then added to the perfusion fluid (0.9% sodium chloride) and, for the remainder of the experiment, was the only substance in the perfusion fluid. In the second group (•, n = 6), BK was added after the first three baseline samples, and then 40 min after beginning knee perfusion, a noxious electrical stimulation of the hindpaw (ES, 25 mA, 0.5 msec. pulse duration, 1 Hz) was applied continuously for the remainder of the experiment. B, Effect of electrical stimulation on PAF-induced PE in the rat knee joint. In both groups of rats, baseline PE was established in the first three samples. In one group, PAF (35 nm; ○, n = 6) was then added to the perfusion fluid (0.9% sodium chloride) and, for the remainder of the experiment, was the only substance in the perfusion fluid. In the second group (•, n = 8), PAF was added after the first three baseline samples, and then 40 min after beginning knee perfusion, a noxious electrical stimulation (25 mA) was applied to the hindpaw continuously for the remainder of the experiment. In this and subsequent figures, data are presented as mean ± SEM ofn values, and ordinate is absorbance of light at 620 nm. After a drug is added to the perfusate, it is present throughout the experiment.