Direct effects of trimetaphan on the dog mesenteric artery and saphenous vein

Direct vascular effects of trimetaphan camsylate were studied in the dog mesenteric artery and lateral saphenous vein; vascular strips were suspended in normal Krebs-Henseleit solution and contraction produced by phenylephrine 2.4 X 10(-6) mol litre-1. Both vessels were relaxed by trimetaphan, maximal relaxation being obtained at the concentration of 1.3 X 10(-3) mol litre-1; this effect was more marked in the vein strips. Calculated ED50 for the relaxing effect of trimetaphan was not significantly different between artery and the vein. It is concluded that the sensitivity of arteries and veins to trimetaphan is similar, but that this effect cannot play a significant role in the production of controlled hypotension.